The present study was conducted to investigate the relationship between the gonad maturation of grass carp, Ctenopharyngodon idella and the changes of pituitary gland cells types coincides with oogonial development and their changes of fatty acid profile and isoenzyme electrophoresis. Five categories of oogenesis are detected such as immature, maturing, ripe spawning and follicular atresia. The pituitary gland has possessed six different kinds of cells. In the rostral pars distalis (RPD), two acidophilic cells types are distinguished; adrenocorticotropic hormone secreting cells (ACTH) and prolactin hormone secreting cells (PRL). The proximal pars distalis (PPD) exhibited two basophilic cell types include gonadotropic hormone secreting cells (GTH) and the thyrotrophic hormone secreting cells (TSH). During ripe stage, the gonadotrophic cells attained the highest changes of the GTH cells explained by increase of cytoplasmic secretory granules. The saturated fatty acids contents reached the maximum peak value and ranged from 38.45% to 39.19%. While unsaturated fatty acids (UFA) ranged from17.09.1% to17.49% and polyunsaturated fatty acids (PUFA) become 43.54% to 44.29%. The most abundant fatty acids were palmitic acid (C16:0), stearic acid (C18:0) in case of SFA, oleic acid (C18:1 n-9) in case of MUFA, linoleic (C18:2 n-6) in case of omega6 and docosahexaenoic (DHA) and acid (C22:6 n-3) Eicosapentaenoic (20:5n-3) (EPA) in case of omega3. The assayed isoenzymes electrophoresis was altered during the ovarian development. The authors finally concluded that there is a gradual change in the pituitary of endocrine cells parallel with changes of follicular development and assessed by alterations of isoenzyme electrophoresis and fatty acids content.