By analysed the climate data in Chang-wu plateau,we found that 1991 is the most serious dry year in near sixty years,we also made a yield forecast of winter wheat in the different earth condition with soil moisture-precipitation in growth period yield model，the conclusion is: the highest yield of winter wheat is 150kg/mu，the lowest yield is 100kg/mu,The yield will reduce 55%-70% next year than the year of high yield.