To determine the current reproductive population composition and reproductive performance of Coilia nasus, 144 fish samples were collected from the South Branch of the Yangtze Estuary from April to June 2021. The individual size, sex ratio, gonadal development stage, conditional factor (K_n), gonadosomatic index (GSI), and fecundity (F) were analyzed. The mean total length (TL) and body weight (BW) of all individuals were (318± 34) mm and (97.16±32.05) g, respectively. Based on a comparison of the months, April had the largest individual size composition. A total of 128 female (88.9%) and 16 male (11.1%) fishes with an overall sex ratio of 8∶1 (female: male) were collected, and female fishes were dominant. The composition of the gonadal development stages for female fishes differed in different months, and the ovary maturity of the individuals in April was mainly in the phase II stage. K_n was the same in different sizes and months, both close to or greater than 1. GSI increased gradually with the continuous development and maturity of gonads from April to June and reached the highest in June. The fecundity was found to vary from 29908 to 74041 eggs, with an average of 51073±11302 eggs for the selected mature fishes. A positive correlation was found between F and TL, F and BW and and between F and gonad weight (GW). The correlation between F and GW was the largest (R² =0.619), followed by that between F and TL and F and BW. These findings could be used to determine the overall reproductive population distribution of C. nasus in the Yangtze Estuary. Collectively, these results provide basic data and a theoretical basis for later protection, management policy-making, and planning adjustment for this species.