To reveal the fish diversity and alien fish invasion status of 4 lake areas of Lake Xinghu (Lake Zhongxin, Lake Xiannv, Lake Bohai and Lake Qinglian), fish resource survey was conducted from March to April 2023. Index of relative importance, species diversity index, Jaccard similarity index, nonmetric multidimensional scaling (NMDS), abundance-biomass comparison curve were used to analyze the species composition, dominance, distribution patterns and diversity of fish in this study. A total of 23 fish species were captured in this survey. There were 11 native fish species such asCirrhina molitorella ,Carassius auratusandHypophthalmichthys molitrix , 12 alien fish species such asPterygoplichthys pardalis ,Prochilodus lineatusandCirrhinus mrigala . Alien fish species had an absolute advantage in terms of percentage (52.17% cumulative proportion), biomass (74.94% cumulative proportion), abundance (77.05% cumulative proportion), and index of relative importance (79.24% cumulative proportion).Pterygoplichthys pardalis ,Prochilodus lineatus ,Sarotherodon galilaeus ,Oreochromis niloticus ,Coptodon zilliiandCirrhinus mrigalaare high-risk invasive fish with stable populations. If not being controlled, they would have a significant impact on the native fish and ecological environment of Lake Xinghu. Among them,Pterygoplichthys pardaliswas the absolute dominant species with the highest ecological risk. The similarity analysis results showed that the average Jaccard similarity index value was 0.70, which was “similarity” level, indicating that the fish communities were relatively similar at various 4 lake areas; The W value of community disturbance analysis was close to 0, indicating that the fish community of Lake Xinghu was at a relatively low level of human disturbance. The results of species diversity indicated that the overall species diversity in Lake Xinghu was at a relatively normal level, while the fish species diversity in Lake Zhongxin and Lake Qinglian was higher than that in Lake Xiannv and Lake Bohai. At present, the most severe ecological hazard in Lake Xinghu is alien fish invasion, rather than direct human interference.