The procedure to visit to China has been changed from 1st December. You need ” Health code” to flight.

You need the SARS-CoV2 PCR test and Antibody test within 2 days before your flight. Then, you will submit the double negative certificate to get ” Health code”.

Please check below LINK.

http://www.china-embassy.or.jp/jpn/sgxw/t1836108.htm