Considering the different effects of soil moisture and precipitation on winter wheat in different growth stages, the calculation method for winter wheat moisture suitability is established in this paper. Then the paper further constructs a climate suitability model of winter wheat combining the calculation models of winter wheat temperature suitability and sunshine suitability. Using the correlations between climatic suitability under different periods and meteorological yields of winter wheat, climate suitable index of winter wheat from sowing to some time in the growing period is established by weighted average. Making use of historical maximum, minimum and average climate suitable index and the observed test data of winter wheat, the diagnostic threshold of climate suitable grade from winter wheat sowing to a growth stage is set up, and then based on this diagnostic threshold, three diagnostic indicators of climate suitable grade in Hebei, Shandong and Henan Provinces are built. The results are significant for improving the quantitative evaluation of agrometeorological service