David - don't be satisfied!
Thanks for this essay. As you said, it’s still much too long, at 362 words, and the sentences are very long.
Write no more than 300 words, and try, try, try to get the average sentence length down to between 12 and 15 words. Every time you hit 20 words, alarm bells should starting ringing, and definitely try to avoid sentences longer than 25 words. Add a handful of short sentences.
In fact, for this essay, I will focus on shortening and simplifying only!
Shorten/Simplify
You wrote:
At the present age, as the technology developing rapidly, creative artists tend to have increasingly enormous approaches to deliver their sentiments, such as via film, music and pictures etc. (29 words)
Here's one suggested rewrite:
Today, [with the growth in technology] artists have many new ways to create film, music, pictures and other artforms. (14 words/19 words)
However, this opening sentence seems to be about technology and artists. Keep to the topic! Go straight to the topic. Where is your opinion or information about restrictions or freedom?
Whether they should expressing their idea freely and allodially has evoked widespread argumentation among the general public.
I’ve no idea what 'allodially' means.
The last part of the sentence is overused, and is generally untrue in any case. Most people don’t care about artists or what they do. Most people could barely name a single living artist. Avoid this structure, or make it fresh.
Where’s your thesis sentence? What is the poor reader going to learn in 362 words?
Here’s a more relevant introduction.
With technology, artists today are able to reach huge audiences. But does this increased market for their ideas mean unlimited freedom of expression or more responsibility? In this essay, I will explain why I think artists should be able to work without restrictions. (43 words, 3 sentences, average 14.7 words per sentence)
Paragraph Two
Paragraph Two is far too long. If you are using a four-paragraph layout, put the side you agree with last in the body:
- Intro
- Other people’s opinion
- My opinon/side
- Conclusion
Make the two body paragraphs similar in length.
Shorten/Simplify
You wrote:
Some individuals hold the idea that creative artists should have the right to express freely, namely without any barriers. (19 words)
Here’s one possible rewrite:
Some individuals believe that creative artists have the right to express themselves without barriers. (14 words)
You wrote:
Doubtlessly, the world tends to be incrementallyclose which thanks to the internet. (13 words)
Here’s one possible rewrite:
- The world is getting smaller, thanks to the internet. (9 words)
- The internet has made the world smaller. (7 words)
Don’t use ‘tend to be’ in any more essays. It tends to be weak and ineffective and it tends to undermine your arguments. You’ve already used it twice, and we are only in Paragraph Two.
You wrote a 49-word monster:
Everything could be conveyed immediately and thoroughly through it regardless of when and what the information we required; therefore, even if the creative artists are forbidden by the authorities to express their own opinion via various media (e.g. websites, pictures, videos etc.), individuals could achieve the truth as well.
Here's a possible rewrite:
Despite government control, users can find anything they want on the internet. This freedom is a godsend for artists. (19 words, two sentences, average 9.5 words per sentence.)
You wrote:
We are living in a democratically equal rather than conservatively feudal society, thus interfering the freedom of expressing is undoubtedly inhumane. (21 words)
Here’s one possible rewrite:
Most of us live in democratic societies where freedom of expression is guaranteed. (13 words). OR
Freedom of expression is guaranteed in most democracies. (8 words)
You wrote:
Furthermore, the intention of speaking candidly is similar compare to brand storming which would enhance the capacity of solving questions. (20 words)
Just as brainstorming helps to solve questions, being able to speak openly helps to build a better society. (18 words)
You wrote a 33-word monster:
Frequently, creative artists are influential, if they convey opinions in their works; it would produce tremendous influences to the society and impose the authorities to revise their politics which are not working smoothly.
Don’t use complicated punctuation. Full stops and commas are plenty, thanks.
Here’s one possible rewrite:
Creative artists can influence society, encourage authorities to revise policies, or even cause political change. (15 words)
You wrote:
Specifically, some artists perhaps accept bribes from some intelligence agents who demand them to deliver unreal opinions in their works in order to misleading the citizens. (26 words)
Don’t start so many sentences with adverbs and phrases ('Frequently,' 'specifically,' 'moreover,' 'admittedly,' 'undoubtedly,' etc). One or two per paragraph is fine. Have a look at the official descriptors for IELTS Task 2 Writing (public version) here, under “overuse of cohesive devices” in Coherence and Cohesion.
Here’s one possible rewrite:
Some artists accept money to deliver government propaganda. (8 words)
You wrote:
Admittedly, this phenomenon can be existed to some extent while the majority of citizens have the ability to distinguish the accuracy of it. (23 words)
No. More. Adverbs. At. The. Start. Of. Sentences. Here's one rewrite:
Most people today, however, can see through propaganda. (8 words)
Conclusion
You wrote:
For instance, satisfying the demand of citizens and improving the efficiency of governments. Hence, I am totally support the idea of first group.
The first sentence is not a sentence. It’s a fragment. Read more about Fragments or Comma Splices. The last sentence makes the reader go back…. and back…. and back. What group? The first group? Where?
Never make the reader go back. The reader is a goldfish, and your job is to guide him or her forward to the end. Do not make the reader think, and do not use words like “the first group” or “latter” or “respectively” or “former.”
Here’s one possible rewrite of your entire conclusion
There will always some tensions when people express themselves freely. However I believe encouraging the public to think and keeping governments in check more than compensates for a few arguments. I hope that artists continue to provoke us and make us look at life differently.
Before your exam, practice writing and rewriting and editing sentences until you pare them down to bleeding stumps. There should be no fat, no extra words, no fluffiness, no 'tend to be,' no complicated punctuation. Add a couple of links in each paragraph. Write only 300 words. You'll be fine. 
Ernest Hemingway
Don't worry about short sentences making your writing look simple. Ernest Hemingway, famous for his short, unfussy style, rewrote the last page of his novel "A Farewell to Arms" thirty-nine times before he was satisfied. He then won the Nobel Prize for Literature in 1954.
Simple to understand, however, does not mean simple to write.