Throughout the 1920s criminals joined together in gangs. By 1927 the various bands had consolidated as the Green Gang with 100,000 members in the city. The influence of Green Gang grew following the coup of April 1927, partly due to the central role it played in events, but also due to the personal friendship between its leader Du Yuesheng and Chiang Kai-shek.

The Green Gang dominated the opium trade as well as a large percentage of the gambling dens and night clubs. In addition to these, the gang ran a protection racket against shopkeepers and organized kidnappings for ransom. The Green Gang was also a major factor in the recruitment of workers and had considerable influence on working life in general. Usually the doormen and foremen at the factories were members of the gang. Likewise, purchases of children for child labor and prostitution was part of the business of The Green Gang.

The success of The Green Gang was in no small part thanks to its utility for the white rulers of the concessions. Leading French officials in the French Concession accepted large bribes. The concession also employed the gangsters as part of its police force and several mob bosses were part of the city council or held key civil service positions.

Du Yuesheng also maintained close ties to the American leadership. Du approached the American administration in the days before Chiang Kai-shek's coup against the Communists and the unions on April 13, 1927, and was granted permission to operate in the International Settlement in exchange for eliminating the Communists.

In the years following 1927 Du Yuesheng amassed further power and in the 1930s he became one of the great business magnates of China.