[6] Beginning in the 1930s, Sun Yu began a collaboration with the leftist film studio, Lianhua, where he became one of the core group of "socially conscious" directors along with Cai Chusheng, Fei Mu, and others.

[6] While with Lianhua, Sun directed some of his most lasting works, including Wild Rose (1932), Loving Blood of the Volcano (1932), Daybreak (1933), Little Toys (1933), and The Big Road (1934).

[6] Upon the end of the war, Sun Yu began preparing for his most important production yet, a biographical epic of the Qing Dynasty educator, Wu Xun, who spread literacy among the common people.

Sun's last major work, The Life of Wu Xun was made with the Kunlun Film Company and starred one of the top actors of the day, Zhao Dan, in the titular role.

In 1985, thirty-five years after the release of The Life of Wu Xun, members of the Chinese politburo finally admitted that Mao's campaign, and the criticisms that it instigated against the film, was essentially baseless.