On this day, 94 years ago, on February 18, 1931 (January 2, 1931 in the lunar calendar), Zhang Jingsheng, a disseminator of sexual science, suffered unfair treatment. In February 1931, Dr. Zhang Jingsheng resigned as a professor at Peking University and returned to his hometown to live in leisure. In recent years, Zhang Jingsheng, a professor at Peking University, wrote an article in newspapers and periodicals advocating the introduction of Western sexual science in China, and then taught sexology on the platform of Peking University. This move pioneered the atmosphere of the Chinese people. Zhang Jingsheng, a native of Guangdong, participated in the Revolution of 1911. He studied in France for many years with Cai Yuanpei, Li Shizeng and others and obtained a doctorate in philosophy. After returning to China, he taught at Peking University. He deeply felt that people's ignorance of sexual knowledge led to psychological flaws, so he spent great efforts to design questionnaires, collect first-hand information about sexual experience from society, and wrote "The History of Sex", which became the first monograph written by China on the history of nature. As soon as the book was published, it was besieged by both official and unofficial officials. At the Nanjing Education Conference, Song Ziwen criticized Zhang Jingsheng for advocating "disorderly love" and "fornication", while Lin Yu called Zhang's book "a very decadent book." Under pressure from all parties, Peking University had to cancel its appointment of Zhang Jingsheng. Zhang suffered this blow, depressed and returned to his hometown. Zhang Jingsheng was also the first scholar in China to propose family planning. He once wrote to Chen Jiongming to put forward the idea of family planning, but Chen Jiongming himself had more than ten children and thought that Zhang Jingsheng was mocking him, so he avoided seeing him.