Not mean that.

No one will cancel your green card (GC). If you stay outside US for more than 6 months and less than one year, the CBP officer normally takes a note on your paasport and this will not affect your GC. Unless you will go forth and back between China and US frequently (in this case the CBP noramlly give you warning and ask you to get the reentry permit for the next time travel), you do not need to do anything at this point and nothing needed to worry about.