Can anyone please tell me where can find free piano sheet from internet?  

I can't help you with the Chinese pages, but I have bookmarked a ton of websites over the years that offer free sheet music. Almost all of the files are PDFs so you can download them and save them to your computer or print them off. Some of the websites require you to sign up, but they are all free. Not sure what kind of music you are looking for, but here are some of my favorite websites for acquiring the free music anyway:

Warren Trachtman's Ragtime pages: http://www.trachtman.org/ragtime/musicbooks.htm

PianoFiles - lots to explore here: http://www.pianofiles.com/

This one also has duets: http://www.8notes.com/piano/

This one is fabulous - LONG list of composers: http://imslp.org/wiki/Category:Composers

And then this one is a collection of sites, and they also have a newsletter worth signing up for: http://www.freesheetmusicguide.com/pianopicks.htm

The other suggestion I have for you is to buy some simple software that converts midi files into piano music. I have MusicTime Deluxe, and it is REALLY easy to use. The reason I suggest this is because there are millions of free midi files all over the Internet that are available for download. They can be converted into sheet music with one click using the software. The best part is that if you have your computer monitor anywhere near your piano, you can read the music from the computer screen and you don't have to worry about turning the page, because the computer does it for you. Just set the tempo, and play away!