Shiyun, there is a continuity problem within your essay. It is very disjointed and erratic to follow as an introductory story. You need to develop certain portions of the essay and delete some portions in order to create a more interesting and truly informative introduction essay. Let's start at the beginning.
When you answer the first prompt in two sentences, try to integrate it into your introduction. Don't leave it hanging as a stand alone part of the essay. It would really be more interesting to read such a flawless integration of your career plans in relation to your public introduction. You can still keep it at 2 sentences, you just need to make it feel like a part of the essay in order to make the essay feel more fluid when the reviewer reads it.
You don't have to go all the way back to elementary school in order to introduce yourself. Jump forward to the reasons why you were inspired to pursue studies in accounting and customer analysis instead. Stories from such a young age will only serve to drag your introduction down since it is in no way connected to your current course and career plans. The tendency will be to bore your classmates with irrelevant information. The most interesting part of your essay as I see it is the following portion:
With limited channels of capital raising, the Chinese financial system has yet to hit maturity to balance out the labor-intensive small firms,which have a great comparative advantage in the world. This drawback is enlarging the wage gap in China as bigger firms have greater chances to raise money from banks. Thus, I am eager to learn how a perfect financial market works by continuing my study in America.
This is the portion that I believe you need to open your introduction with. Doing so will immediately gain the interest of the listener / your classmates and also inform them about your plans after graduation at the same time (with the proper paragraph development). I would continue to discuss the influences I had in the field of finance both from China and the U.S. and segue that talk into the conclusion as to why I chose to come to the United States to study.
I realize that this is still an essay draft on your part and it has room for improvement. I suggest that you work on developing the story of the essay for now. Don't worry about the grammar corrections that need to be done at this point. It is useless to address those issues if the essay is not ready for finalization yet. Good luck!