Ou boy! This is a tricky issue. If you want to do it in the U.S., you need to:
1) Make a copy of the passport.
2) Go to a place which provide the notary service (gong zheng) which could be a bank, an atturney's office, or a Notary Public. Have it notarized as a genuine copy of the original document.
3) Send the notorized copy to the Chinese Consulate which has the "juricial power" over your area, to have the Consulate to notarize the stamp put on the copy is valid.
I do not know how restrict on the Chinese side. So you'd better ask them what kind of copy is acceptable, and follow their "order".
