-The adopted child can apply for B-2 visa to enter USA to live with you. The child can renew his/her B-2 status gain and again. If the child does not keep his/her B-2 status, then you can become a US citizen to sponsor his/her green card after he/she lives with you for at least two years.
The critical thing is that you had better not become a US citizen before the adoption procedure is completed as 柠檬椰子汁 suggested because the adoption procedure is much simpler for a Chinese citizen to adopt a child from China than for a US citizen to do it.