The grass carp,  Ctenopharyngodon idella, is an exotic fish in the Egyptian fauna. It is used as a protein source and for biological control of aquatic weeds grown in the water of both advanced and developing countries. Spawning was done by injection with hormone or pituitary extract of another common carp due to the lack of spawning in captivity farms. In May, the gonadosomatic index (GSI)  increased and reached the highest value in May (17.645±0.381) which decreased steadily and reached the minimal value in October (0.161±0.034). The water temperature during this time is ideal and ranged from 25 to 28 C^o. The annual ovarian cycle is subjected to successive developmental periods.  This involves the primary and secondary growth process of ova formation changes such as yolk deposition and cytoplasmic vacuolization contributing to its maturation. Owing to the lack of spawning, several studies have been carried out on follicular atresia that needs to be explained. This study was undertaken to explain the aspects of this process by analyzing the environmental factors in correlation with investigating the ovarian wall at a light and ultrastructural level.