Abstract: MAO Zedong's thoughts developed greatly from 1918 to 1921. Before 1918, MAO Zedong did not understand Marxism. After May 4^th Movement, His thoughts changed. He not only advocated “the great union of the people” but also publicized “the anti-feudal democratic revolutionary thought”. MAO Zedong opposed bloody revolution at first, and then changed this idea to support “fierce communism”. From the summer to December in 1920, MAO Zedong gradually became a firm Marxist. He was engaged in establishing the Communist Party of China, believing that China definitely needed a new type of Party to lead the anti-imperialist and anti-feudalist revolution. The First National Convention of the Communist Party of China absorbed anti-imperialist ideas, including his thoughts, and formulated the anti-imperialist revolutionary program. All in all, MAO Zedong knew and accepted Marxism step by step, and recognized the necessity for China to take the October Revolution Road. The establishment of the Communist Party of China was the inevitable result of the ideological change of intellectuals represented by MAO Zedong. The pioneers of Chinese working class “studied Marxism-Leninism and founded the Communist Party of China”.