As many people from Western countries perceive that Chinese are very sensitive to numbers; I'm not an exception either.
I was introduced to the world of business
since I was nine at age nine
through which I can lay a solid foundation in advance for not only my Master or Ph.D but also my future career
Why not "through which i can lay a solid foundation not only for my Master and Ph.D, but also for my future career"
Among all the opportunities Tepper offers, I'm especially interested in the Undergraduate Business program, the BSBA MBA 3/2 program, and the summer internship opportunities, through which I can lay a solid foundation in advance for not only my Master or Ph.D but also my future career and apply the business principles I learn in class to the real-world consulting projects.
You could probably cut this sentence into 2 or 3 short sentences.
The small size class is another feature that fascinates me.
You should start a new paragraph here.
One more suggestion is to vary your sentence length. Many of your sentence were long. Add a few short sentences or make split some sentences into smaller ones.
Overall, I think this is a solid essay. You have provided good reasons for CMU.