Climatic factor is one of the important causes impacting marine fish biomass. The data of total yield and fishing effort of East China Sea and four climatic factors which were sea surface temperature (SST), monsoon, typhoon and runoff from 1951 to1984 were added to Fox surplus yield model to optimize catch per unit effort (CPUE). Climatic factors and parameter were analyzed by linear and exponential regression model with stepwise method respectively. The results showed that SST and summer monsoon were selected as the new parameters to modify parameter . Finally, the linear regression model was recognized as the most optimized model by AIC analysis. In the linear regression model, the coefficient of regression ( values of coefficients were below 0.01, and zero was out of the 95% confidence interval for all coefficients. The simulation effect of the optimized model is much better than original model, which suggests that SST and summer monsoon significantly impact commercial fishes in East China Sea, and it’s very necessary to consider the influence of climatic factors when doing Fox surplus yield assessment.