In order to understand the species composition and diversity characteristics of the main fish communities in Dianshan Lake, environmental DNA technology was used to analyze the species diversity of fish in Dianshan Lake. The results showed that a total of 7 orders, 12 families, 36 genera and 43 species of fish were detected in the environmental DNA samples from 10 stations in Dianshan Lake, of which 24 species were detected in June (summer) and 32 species were detected in November (autumn). Most of the species were found in the traditional fishery resources investigation of Dianshan Lake. Among them, Coilia nasus, Carassius auratus, Acheilognathus macropterus, Culter alburnus and Mugil cephalus were the main species. The α diversity analysis showed that the average values of Chao 1 index, Observed species index, Shannon diversity index, Simpson index and Pielou evenness index in Dianshan Lake in autumn were higher than those in summer. The analysis of fish species difference among sites showed that the sites with higher diversity and richness were S1, S2, S3 and S5, which were all sites with higher primary productivity and less human disturbance. The results show that the environmental DNA technique is highly sensitive and can be used as an effective supplementary method for the survey of fish species diversity in Dianshan Lake.