To study the gonad development of spotted knifejaw (Oplegnathus punctatus), this study focuses on the development and differentiation process of spotted knifejaw gonads with histological methods. The results showed that O. punctatus is a differentiated gonochorist. Its spermary is lobular in the structure.Its development can be divided into six stages. Under the culture at 24-26℃, the full length of fish 120 days after hatch ranged from 56.1 to 64.5 mm, and spermaduct formed, indicating the beginning of testis differentiation. Seminal lobule formed 180 days after hatch, indicating the accomplishment of anatomical differentiation of testis. Meanwhile, the appearance of primary spermatocyte indicated the beginning of cytological differentiation of testis. The development of female gonads can be divided into six stages. Under the culture at 24-26℃, the full length of fish 90 days after hatch ranged from 30.4 to 49.5 mm, and clusters of oocytes appeared, indicating the beginning of anatomical differentiation of ovary. Ovarian cavity was observed in presumptive ovary 150 days after hatch. The appearance of primary oocyte 180 days after hatch indicated the beginning of cytological differentiation of ovary. This study showed that the anatomical differentiation timing of ovary was earlier than that of testis in O. punctatus; while the cytological differentiation of ovary and testis was synchronized.