Thanks for the essay Chao and for the comments ChrisLuke!

The essay is nice and short at 269 words, and it's fairly easy to read, although the 20-word average is too high. I'd really try hard to write shorter sentences. ChrisLuke has identified three or four sentences which could be split into two -  there are more.

One sentence which puzzled me (and ChrisLuke) was this one

In addition, what effects would the food produced by modifying their genetic makeup have on human beings are still unknown.

It's got a word-order problem. Here's a possible rewrite:

In addition, what effects the food produced by modifying their genetic makeup would have on human beings are still unknown.

Or we could simplify and shorten it a little:

In addition, we still don't know the effects of genetically modified food on our health.

Thesis Sentence

Chao, I would definitely add a thesis sentence to your intro. Your intro is too short and the reader is puzzled about what you are going to do in the essay. You can read more about Thesis sentences here.

Watch for wordy sentences, as ChrisLuke suggests. Here's one which rambles on a little:

Also, more kinds of food have been offered in the market, which gives people more choices when they are deciding what will be served for dinner or lunch.

It's 28 words long, which is just too long. We could squeeze more ideas in if we eliminated unnecessary words:

Also, more kinds of food are available, so consumers have more choices. This could lead to healthier diets with more variety, and fresh foods all year round. 

Twenty-six words AND two extra ideas!

Conclusion

I would also write your conclusion as two or three sentences. One sentence has to do too much work. You can read more about conclusions here.

Break this 52-word monster up into several sentences in which you summarize both sides, give your opinion and look to the future.

Overall

Chao, you have a nice style in your writing. I hope you get some time to comment on some of the other essays here. Lots of new ones, so plenty to choose from! People really appreciate it! 

Thanks again to both of you!

Just some comments:

1. Modern technology has influenced the food industry a lot. With fertilizer(s,), farmers can produce more food within the same size of field(in the same field?) as before. With the modifying of genetic makeup of some plants (you mean genetically-modified produce or food...), we can get more types of food.

2.With the crop yield increased(hmmm), the price of vegetables and meats has been decresed(decreased)

3. Also, more kinds of food have been offered in the market, which gives people more choices when they are deciding what will be served for dinner or lunch.

(Chop off.chop off..chop off....lol)

4.  First and foremost,? hmmm...this is not incorrect but i reckon "first" or first of all is better.......first and foremost basically are the same.....unnecessarily wordy.

5. First and foremost, the wide use of pesticedes will be devastating to the balance of eco-system and it will cause diseases among human beings because some pesticides can be left on the fruits or vegetables and hard to clean

(First of all/ First, the extensive use/widespread use of pesticides are devastating to ......... (full stop).  it will...... )

by the way, you wrote that it is devastating to the balance of ecosystem and causes diseases........because some pesticides can be left on the fruits or vegetables and hard to clean????????  the reason seems only for causing diseases....

6...what effects would the food produced by modifying their genetic makeup have on human beings are still unknown. Scientists need more time to find out the long term effects before they can be sold in the food market...(hmmmm rewrite this sentence?)

7.green? u mean environmentally-friendly?

Modern technology has influenced the food industry a lot. With fertilizer, farmers can produce more food within the same size of field as before. With the modifying of genetic makeup of some plants, we can get more types of food.

The advantages of these changes are obvious. With the crop yield increased, the price of vegetables and meats has been decresed. Thus, people can invest more money in education or entertainment and this is the sign of the improving of people’s living condition. Also, more kinds of food have been offered in the market, which gives people more choices when they are deciding what will be served for dinner or lunch. But before, people can only had few choices on the kinds of food especially in winter time.

However, there are also some disadvantages of these changes. First and foremost, the wide use of pesticedes will be devastating to the balance of eco-system and it will cause diseases among human beings because some pesticides can be left on the fruits or vegetables and hard to clean. In addition, what effects would the food produced by modifying their genetic makeup have on human beings are still unknown. Scientists need more time to find out the long term effects before they can be sold in the food market.

Overall, the modern technology has indeed led to some good changes in the food industry, such as the lower price and new types of food, but the scientists still have much to do to make the changes more green in order to benefit the human beings and environment in a long term.