Abstract: The Pearl River Delta river network (PRDRN), with its unique subtropical geographical pattern of "three rivers converging and eight outlets to the sea", is one of the most fish-diverse waters in the world. In order to understand the fish diversity and spatial distribution patterns in the river network of the Pearl River Delta, and to provide data support for the conservation and sustainable development of river network fish diversity, this study calculated the Shannon-Wiener diversity index, Pielou's evenness index, and Margalef richness index to characterize fish diversity. Non-metric multidimensional scaling (NMDS) and redundancy analysis (RDA) were used to explore the distribution characteristics of fish in the Pearl River Delta river network and their relationships with environmental factors. The results showed that a total of 157 fish species were collected, belonging to 16 orders, 57 families, and 124 genera, with Perciformes being the most numerous (78 species), accounting for 49.68% of the total fish species, followed by Cypriniformes (30 species), accounting for 19.11% of the total. A total of 17 alien fish species were surveyed, among which Oceochromis nilotica had the highest numerical proportion and Prochilodus lineatus had the highest weight proportion. Among all sampling sites, the Hengmen River section in Zhongshan had the highest diversity index (3.37), evenness index (0.78), and richness index (8.56). NMDS results showed that fish in the Pearl River Delta river network can be divided into three communities: Community 1, dominated by pelagic and demersal-pelagic fish such as Hemiculter leucisculus, Megalobrama terminalis, Hypophthalmichthys molitrix, Aristichthys nobilis and Squaliobarbus curriculus; Community 2, composed mainly of benthic fish including Misgurnus anguillicaudatus, Glossogobius giuris and Cynoglossus trigrammus; Community 3, represented by typical estuarine fish such as Clupanodon thrissa and Coilia grayii. RDA results indicated that salinity, precipitation, and water temperature had significant effects on fish communities. This suggests that the fish resources in the Pearl River Delta river network are abundant and fish diversity is relatively good, but species invasion is relatively severe, and the relative historical resource quantity has decreased considerably. Fish populations in the river network are divided into three groups, and salinity, precipitation, and water temperature are the main factors influencing the spatial differences of fish communities in the Pearl River Delta river network. The study clarified the fish diversity, spatial distribution patterns of communities, and related influencing environmental factors in the Pearl River Delta, providing a scientific basis for the conservation of fishery resources and sustainable development.