Thanks for this essay. Sorry I was busy doing other things and a lot of new essays have been posted!

Word Choice/Word Form/Usage

• In present days → today
• It is not easy to say if this trend good or not. → It is not easy to say if this trend is good or not.
• During grow up, young people may feel that → While growing up, young people may feel that
• I think it is impact on the family → I think it impacts the family  OR  I think it has an impact on the family
• They may worry their children → They may worry about their children
• If this anxious last too long, it may lead to some mental disease  → If this anxiety lasts too long, it may lead to some mental disease

Generic Sentences

These sentences could be used in any essay.

• I will discuss both sides as following.
• It is not easy to say if this trend is good or not.

Try to make every sentence unique to this essay.  Avoid generic or standard sentences.

Paragraph Two: Topic Sentence

You wrote:

People can gain better education and more job opportunities in big cities.

This sentence is correct, but it’s a little confusing as a topic sentence. What about the millions of people who already live in cities? You could live in New York or Hong Kong and still move to another city to work or study.  Try to make a topic sentence that summarizes the entire paragraph.

Punctuation: Comma Splices, Fragments, and Unnecessary Commas

You wrote a run-on or comma splice sentence (read more about  Comma Splices and Fragments here).

•  they have the ability to live by themselves, no need to rely on parents all the times.

Here’s one possible rewrite with the comma removed. You could also write a separate sentence.

They have the ability to live by themselves and they don’t need to rely on parents all the times.

Here’s another comma splice:

• We are not alone in the world, single person cannot finish one big project

Here’s one possible rewrite:

We are not alone in the world. A single person cannot finish a big project alone.

Here’s a third comma splice:

• Young people should understand the feeling of their parents, try to give more calls to them and take care of them.

Here’s one possible rewrite:

Young people should understand their parents’ feelings. They should try to call them and reassure them.

Here’s a fourth one:

• They need to solve all the problems by themselves, leaving home to study or work in other places can help young people

I will leave this one to you to fix.

Here you have unnecessary commas:

• Living with friends, who from different places, can help young people

The commas are not needed here. If in doubt, leave commas out.

Living with friends from different places can help young people.

You wrote a fragment here:

As all the parents want their children can get better education and find a better job in the futrue.

Try to avoid starting sentences with ‘and,’ so,’ ‘but,’ for,’ ‘because’ and ‘as.’

All parents want their children to get a better education and find a better job in the future.

Conclusion

You wrote:

• In sum, I think the advandage of leaving home to study or work on other places are more than its disadvantages.

Why are they better? This semi-generic sentence forces the reader to go back and remember what you wrote. Why not summarize?  It can mean a slightly long sentence, but it’s more interesting:

In sum, I think leaving home to study or work can make young people more independent and give them more experience.

Verb Tense

The parents may feel lonely after their children left home for study or work. → The parents may feel lonely after their children leave home for study or work.

Overall

Overall the essay is OK. The layout is simple and clear. I’d like fewer generic sentences, and perhaps more ideas in Paragraph Three. Try to have a better topic sentence – one which summarizes all the ideas, not just one or two of the ideas in the paragraph. But watch out for those comma splices, run-on sentences, fragments and punctuation errors. The length of the sentences should warn you that you need to keep sentences short to avoid errors! 

Have a look at the official descriptors for IELTS Task 2 Writing (public version) here, under Grammar and Accuracy and look for the phrase “punctuation may be faulty.”  This is an easy problem to fix, so fix it and get it out of the way.

In present days, a number of young single people leave their hometown to study or work in other places. It is not easy to say if this trend good or not. I will discuss both sides as following.

People can gain better education and more job opportunities in big cities. Because in small cities, there are not enough high quality schools, young people have to attend school in other cities to get better education. During grow up, young people may feel that they have the ability to live by themselves, no need to rely on parents all the times. As parents are far away, they need to solve all the problems by themselves, leaving home to study or work in other places can help young people to be more independent. Moreover, young people can learn how to communicate with other people. We are not alone in the world, single person cannot finish one big project without others' help. Living with friends, who from different places, can help young people to learn how to manage the relationship with others.

What's the disadvantages for this trend? I think it is impact on the family. The parents may feel lonely after their children left home for study or work. They may worry their children. They make the call every day to ensure all the things around their children are fine. If this anxious last too long, it may lead to some mental disease which is bad for health. Though this case should be few. As all the parents want their children can get better education and find a better job in the futrue.

In sum, I think the advandage of leaving home to study or work on other places are more than its disadvantages. But in the meantime, i think young people should understand the feeling of their parents, try to give more calls to them and take care of them.