This paper describes the symptom of black or burning fins, bugeyed and abdominous form which occured in the rearing of grass carp (Ctenoharynogodon idellus)，big head carp (Aristihthys nobilis) and silver carp (Hypopthalmichthys molitrix)in both Hubei and Hunan provinces. According to the results of preliminary research, the syxuptom was probably caused by applying overdose of sodium pentachloranate as a disinfectant in pond, and also by too early stocking the fingerings into the pond before the chemical lost efficacy.From the histopathological analysis, the major reason of the fingerling mortality was, the chronic Corrosion of the skin and xnucaus membrane of gills by the chemical, and finally resulting in the acute attach. The dark pigmentation on the gills axed skin was apparently due to the pathological changes resulted from the long erposure in the high concentration of the chenaival.It is suggested by using quick-lime (2o-25kg/mu) as an antidote in order to improve the pond water and neutralize the residue of sodium pentachlorvphenate.