In order to obtain the characteristics of the temporal and spatial distribution of fish in Chenhang Reservoir,Shanghai, dual-frequency identification sonar(DIDSON)was used in fish resource on April 17th, August 15th, and November 13th, 2019. Fish target analysis model for carry out the extraction and counting of fish targets was established by ECHOVIEW underwater acoustic data processing software. To draw the horizontal and vertical distribution maps of fish resources density and further analyze the spatial and temporal distribution of fish quantity in reservoirs.The result showed:The proportion of small and medium-sized fish (length <60 cm) in Chenhang Reservoir was 80.9%; The body length, density, number and total weight of fish in the reservoir increased from spring to autumn; on the horizontal spatial scale, fish mainly gathered in the southern part of the reservoir, with relatively concentrated distribution in summer and relatively scattered in autumn; on the vertical spatial scale, fish in the reservoir area were mainly distributed in water depth between 2-6 m, proportion is 84.85%. The average depth of fish distribution was 3.89 m in spring, 4.34 m in summer, and 5.12 m in autumn,the vertical distribution of fish in the reservoir area tended to move to the bottom with the seasons. The underwater acoustic detection method and fish target analysis model studied provide useful reference for similar fish resource investigation and analysis, and the detection results provide useful assistance for fish stock management.