From 1921 to 1949, after 28 years of hard exploration and persistent struggle, the Communist Party of China (CPC) finally won the victory of the newdemocratic revolution in the whole country, and created brilliant achievements. Among them, the important revolutionary practice of transforming the subjective world with the thought of “Two Musts” put forward by Comrade Mao Zedong in Xibaipo period, together with the revolutionary practice of transforming the objective world, constituted the grand landscape of the newdemocratic revolution in this historical period, and promoted the major transition of the Chinese history. CPC revolutionary practice of transforming the subjective world with the thought of “Two Musts” has answered the questions and solved the difficulties of the times from three aspects: transforming the bad ideological style and habits in the revolutionary ranks and tempering the revolutionary character of the people’s army; transforming the nonproletarian ideology in the revolutionary ranks and establishing the proletarian world outlook and value of life; and overcoming the “four attitudes” in the revolutionary ranks before and after entering Beijing and establishing the thought of continuing the revolution.