Abstract: Over the past 40 years of reform and opening up， the development of Chinese detective and gangster films is an alternation of police and gangster films and public security films. Appearing first in the 1980s， the public security films have a strong inherent ideological nature，and gradually evolved into a branch of the“ mainstream melody movies”under the principle of“ highlighting the mainstream melody and adhering to diversity”. The detective and gangster films appearing in the 1990s， on the other hand， highlighted entertainment and“ modernity” experience with the modern visual elements and the exotic emotional appeals of cross-border manhunting. In the 21st century， when Hong Kong film directors finally found their access to the ideology of the mainland on the platform of the new mainstream discourse， detective and gangster films are mainly coproductions by movie companies from China mainland and Hong Kong. In the future development of detective and gangster films in China， the public security films will continue to exist as an important form of“ mainstream melody movies”， but detective and gangster films will go in two directions: mainland directors will explore their own styles in detective and gangster film shooting，while Hong Kong-style detective and gangster films will be more universal and inclusive new mainstream melody films.

Key words: Chinese detective and gangster films, public security film, detective and gangster films, ideology, modernity experience