As an idle place of cage culturing, Qiandao Lake has been suffering from a series of problems because of the cage culturing these recent years, which affected the water environment in a certain extent. In this paper, we analyzed the exact water environment affection caused by the cage culturing in Qiandao Lake based on the methods of contrastive detection in and out of the culturing cage, and contrastive detection before and after the application of the cage culturing.