The sex steroid hormones includes17β-estradiol (E2), testosterone (T) and progesterone (P) were studied during the annual cycle of gonadal maturation. The pituitary gland secretes gonadotropin hormone which is used as monitor and control on the secretion steroid hormones from the theca and granulose cells of follicular oocyte. The annual fluctuated in 17β-estradiol (E2) is correlated with the degree of maturation state in the ovary of grass carp as vitellogenesis ceased and the ova reached to the final maturation state, the concentration of E2 decreased to the minimum level 109ng/ml. The testosterone (T) level among the other sex steroid hormones plays an essential role in the sexual maturation. Testosterone (T) fluctuated through the maturation cycle and reached the lowest value at immature state of gonad and measured 1.5ng/ml, however this value gradually increased and peaked in ripe stage to 2.2ng/ml. The value of T decreased to 1.5ng/ml in atretic stage. The fluctuated in the total T level in the serum of grass carp seem to be inconsistent with fluctuation of E2. Progesterone (P) peaked in maturing ovary and measured 12.9 ng/ml and then decreased to 9.2 in ripe stage. Both Follicle stimulating hormone (FSH) and luteinizing hormone (LH) play an important role during the annual cycle for growth oocyte and is necessary for maturation and successful in propagation process.