Based on the grey system theory, the occurring rule of the bacteroidal disease of cage cultured large yellow croaker (Pseudosciaena crocea) in Zhoushan was examined, and the relationship between the disease and environmental factors of surrounding sea waters was investigated. The grey models were established for forecasting the relevant data or incidence of the disease. The grey incidence analysis showed that the incidence of the disease was related to environmental factors in the different extent. Taking water temperature, the suspended solid, inorganic nitrogen and COD as forecasting factors, the GM(1,5), GM(1,4) and GM(1,3) were constructed respectively. Compared these models, the GM(1,3) constructed by inorganic nitrogen and COD had least mean relative simulation error. GM(1,1) was also established for the forecasting of the occurring data of the bacteroidal disease in wider scope, its veracity reached up to 90.5%.