The myxosporidian fauna and myxosporidian epidemic of fingerlings and second year's of allogynogenetic crucian carp of Hubei was investigated by the auther in 1987.3---1988.1. The species component, infection and seasonal fluctuation of the fauna and histopathological changes of the epidemic are the subject of the present paper. 505 specimens of the fish were examined. 36 species of Myxosporidia were found, including a new species of Unicauda. Among the, llspecies were Myxobolus. Myxobolus is the dominant group of the fauna. Some specices of the Myxosporidia manifested obviously seasonal changes of the infection incidence. The type of seasonal changes can be grouped into: high infection incidence in summer; high infection incidence in spring and autumn; seasonal infection; and opportunity of infection incidence. Heavy infection of a few species of the Myxosporidia discovered can cause serious epidemic diseases and histopathological changes occur. Myxosoma sinensis, Myxosoma magna, Thelohanellus fuhrmanni and Henneguya zikaweiensis mainly parasite on/in gills. Hyperplasia of the epithelial cells. atrophy, fusion and necrosis can be observed in the infected secondary lamellar. Myxosoma bibullatum mostly parasites in the heart and causes the muscle of heart inflammation and necrosis. Myxobolus musculi can cause renal necrosis. Thelohanellus hovorkae and Thelohanellus liohoensis can cause pathological changes of the skin infected.