The largefin long barbel catfish (Hemibagrus macropterus) is an economically important fish species in China. Although breakthroughs have been made in the artificial breeding technology of H. macropterus, obstacles such as imperfect broodstock cultivation and low fertilization rates remain. Therefore, it is essential to strengthen research on the reproductive biology of broodstocks of this species. In this study, morphological measurements, histological analysis of ovarian tissues, and enzyme-linked immunosorbent assay (ELISA) of serum were performed to investigate the annual changes in ovarian development and sex steroid hormone levels in female large fin long barbel catfish broodstocks under artificial breeding conditions. The fish used in this study were cultured at the Changshou Experimental Farm of the Chongqing Fishery Sciences Research Institute. From October 2023 to August 2024, 40 female H. macropterus broodstock were sampled every three months with 10 fish sampled in each sampling month. The body weight and total length of H. macropterus used in the experiment were 122.20 to 494.50 g and 26.20 to 44.0 cm, respectively. Individually sampled fish were anesthetized using 100 mg/L MS-222, and their body weight and total length were measured. Blood samples were collected from each fish via caudal venipuncture and allowed to coagulate at 4 ℃ for 12 h. Serum was obtained by centrifugation at 3000 g for 10 min. The ovary samples were dissected and weighed, and the anterior, middle, and posterior parts were immersed in Bouin’s solution for histological analyses. Commercial ELISA kits were used to measure estradiol (E2) and testosterone (11-KT) levels in serum. The results showed that the gonadosomatic index (GSI) of female H. macropterus broodstocks varied between 0.57 and 12.16 throughout the year, reaching its peak (12.16 ± 0.67) in May when they entered the breeding season. In August, the GSI value decreased, and the ovaries began to degenerate. From November to February of the following year, the GSI were not significantly changed compared with that of August, and kept at a low level ranging from 0.57 to 0.82. Based on their morphological characteristics, oocytes in the ovaries of the sampled fish were divided into six stages (I~VI): immature oogonia (I), primary growth (II), cortical-alveolar (III), vitellogenic (IV), mature (V), and degeneration (VI). By comparing the proportion of oocytes in each sampling month, ovarian development was classified into four stages: the initial development stage (November; dominated by stage II and III oocytes), pre-breeding stage (February; with the highest area ratio of stage III oocytes), breeding stage (May; oocytes from stages II to VI occurred simultaneously with stage V oocytes occupying the highest area proportion), and degeneration stage (August; mostly stage II and III oocytes). In the May spawning season, the expression level of E2 in the serum of H. macropterus broodstocks peak at 301.15 pg/mL and then decreased significantly in the subsequent degeneration stage in August. Conversely, the 11-KT content was the highest in August (135.00 pg/mL), which was significantly different from that in the other three sampling months (P＜0.05). These results indicate that the female large fin long barbel catfish belong to the single spawning type, with only one peak in the annual GSI, and the breeding season begins in May. The levels of hematological sex steroid hormones are closely related to the stages of ovarian development and can be used as important indicators to assess the ovarian developmental status of cultured H. macropterus. The results of this study provide a reference for further research on the reproductive regulation of large fin long barbel catfish broodstock and for improving the efficiency of artificial breeding of this species.