Novels about brothels are called narrow evil novels by Lu Xun. At the end of the Qing Dynasty and the beginning of the Republic of China, narrow evil novels constantly appeared in the literary world. It has obvious regional characteristics and characteristics of the times, which constitutes a unique landscape of China's romance novels. There are many reasons for the emergence of narrow evil novels. First of all, it can be said that readers' aesthetic psychology and reading interest determine the development trend of novels. However, the environmental background of this period can not be ignored, and two factors also played a role. First, there are many prostitutes. Second, there are a large number of frustrated literati in the middle and lower classes, and their road to fame and fortune is still bumpy. This contributed to the prosperity of narrow evil novels for a period of time. It has its own development and evolution process. That is, Lu Xun said in "A Brief History of Chinese Novels": "The author's writing about prostitutes has changed three times, first beautiful, then close to the truth, and finally overflowing with evil." Early narrow and evil novels belong to the category of romance novels, and the description of prostitutes is somewhat aesthetic. His representative works include the mirror of flowers, the scar of flowers and moons and the dream of a brothel. The narrow and evil novels in the middle period gradually evolved from romance novels to social novels, and the description of prostitutes gradually became realistic. His masterpiece is Biography of Flowers on the Sea. In the early years of the Republic of China, the description of prostitutes was more or less evil. Almost true, it is also the best work in the whole modern novel. Therefore, this paper intends to compare Biography of Flowers on the Sea with the three earlier masterpieces from four aspects. The specific comparison contents are different ideological tendencies, differences in character description and narrative style, differences in narrative forms, ideals and condemnation. The main purpose of this comparison with Treasure of Flowers, Flower Moon Scar and Dream of a Brothel is to prove Shanghai.