An SST model which is good at predicting offshore-SST anomaly (O-SSTA) has been developed.It is composed of three parts: equations of dynamics, equations of model's physics and equations of affecting factors of O-SSTA.Initial field of SST is prepared for a case of O-SSTA on last decade of July 1994,in which there are a center of warm anomaly in the Huanghai Sea and a center of cold anomaly in the East China Sea to be developing simultaneously. Using the observed atmospheric forcing, the (decade) experiment forecast is made.Forecasting accuracy of warm (cold) anomaly is 32/44 (29/33), the ensemble accuracy reaches R=91% and AMD=0.67℃.The chief affecting factors of O-SSTA for this case are shown, for warm anomaly:(1) solar radiation (weight is 64%),(2) the convergence of warm water(9%),(3)shallow-water effects; and for cold anomaly:(1)pumping of typhoon (44%),(2) entrainment of storm (24%),(3) latent heat(19%),respectively.It is identified that the formation of warm (rnld) anomaly is a slower (faster) process.