When did communism begin in China?

It was in 1949 when Mao Zedong came into power.

Before World War II and the Chinese Civil War (1946-49), when the Chinese Communists under Mao Zedong were able to oust Chiang Kai Shek and the Guomindang (Chinese NAtionalist Party). The new government vowed to create a new china, molded along Marxist lines.