Ctenopharyngodon idella, the grass carp, has a reduced spawning season that extends from April to May. The biological parameters including, length at first male sexual maturity, are represented at a length of 53 cm in which 50% of male grass carp matures. Furthermore, the gonadosomatic index (GSI) increased dramatically from January 0.264±0.08 to a peak in April and reached 2.797±0.333. Microscopically, the immature testes are composed of developing spermatogenic cells, while the ripe tests contain mainly sperms. The interstitial cells are situated between the seminiferous lobules. The adenohypophysis of the studied fish is divided into three regions; the rostral pars distalis, proximal pars distalis, and pars intermedia. The gonadotrophic cells exhibited different degrees of secretory activity and hypertrophy during the sexual cycle. The authors finally concluded that there is a cyclic change in the testicular germ cells parallel with the gonadotrophic cell activity in the pituitary gland.