Abstract: The gonadal development of the alltetraploid hybrids of Carassius auratus red var(♀)× Cyprinus carpio L.(♂)was studied through tissue section The gonadal development was similar to that of Cyprinus carpio and Carassius auratus and could be divided into six stages Both the male and the female fishes could attain sexual maturity The male fishes attained earlier sexual maturity than the female fishes The male fishes attained sexual maturity when they were 150 days old,but the female fishes needed a year The mature coefficient of testis was 1.65%-5.19% and the mature coefficient of ovaries was 9.25%-15.60% The diameter of mature oocyte was 1670-1780μm The diameter of the head of mature sperm was 2.3-2.4μm The breeding season of the fishes was from March to May The study proved that the gonadal development of the allotetraploid hybrids was normal and both the female fish and the male fish could be fertile.