University of Nanking
Li returned to China at the age of 30 and became the Professor of Genetics and Biometry at University of Nanking, his alma mater, in 1943. After World War II, he moved to Beijing for a Professorship of Agronomy at Peking University in 1946, where he finished "An Introduction to Population Genetics" in 1948. The book was the first notable publication where a combination of the ideas of Ronald Fisher, Sewall Wright, and J. B. S. Haldane about population genetics was brought to and made understandable to the academia.