By analyzing thirty years'direct coupling results of a TOGA coupled model it is found that serious “climate drift” phenomenon exists in the model's tropical SST. Based on analysis of heating and cooling terms in the model's SST equations, specially through analysis of heat flux and wind stress, it is pointed out what roles both errors play in “climate drift” phenomenon. In order to check the analysis results, four sensitive experiments have been performed to clarify the effect of heat flux and wind stress on the tropical SST distribution, especially both relative effects for forming western tropical warm pool and eastern tropical cold tongue, as well as relative contribution of zonal and meridional wind stress.