Tissue slicing and enzyme linked immunosorbent assay (ELISA) was conducted to help understand the law of development and the level of sex steriod of cultured Pampus argenteus, and we observed the developmental characteristics of testis and ovary of P. argenteus under breeding conditions and the year-round changes in serum neutral steroids. The relation between gonadosomatic index GSI, hepatosomatic index HSI, condition factor CF and gonad development were also studied. The results showed that breeding females matured at the age of 1 year, and the matured ovary presented in the shape of ">". Nearly half of individuals entered into stage III in November, 33.3% individuals had been developed into stage IV. From December to next January during the winter, about 2/3 individuals degenerated to stage II and developed quickly to stage IV in March. In April, P. argenteus reached stage V and spawned. After spawning, the ovary entered into stage IV. The structure of testis is lobule lumen, and lobular cavities appeared in stage III of testis, and sperm appeared in stage IV. The development of testis was faster than that of ovary, which means "male premature". 20% of individuals reached sexual maturity after 7 months. During the winter, from December to the next February with decreasing temperature, the testis degenerated to stage III and in March the testis developed again, sperms were discharged at different time. GSI of females differed from 0.19% to 12.89%, HSI was from 0.97% to 2.30% and CF ranged from 2.30% to 3.08%. GSI in males ranged from 0.08% to 2.62%, the value of HSI was from 0.73% to 1.83% and CF was from 2.11% to 2.80%. The value of GSI reached the maximum in the stage V, and HSI and CF reached the peak in stage IV. The content of E₂ of female varied from 23.27 to 59.13 pg/mL and the content of E₂ of male was 15.90 to 36.20 pg/mL in different develpomental stages and the value of HSI in females showed significant positive correlation. The content of testosterone (T) in female was from 14.57 to 68.67 nmol/L and that in male was 18.62 to 66.49 nmol/L in different develpomental stages and changes in expression levels of T showed significant positive correlation. Our research shows that the content of serum steroid hormones was closely related to the development of the testis and ovary and could serve as an important indicator to understand the development of cultured P. argenteus gonad in time.