Abstract: Based on winter wheat yield data from 1960 to 2008 in Tianjin,the main meteorological factors and their trends,which affected winter wheat yield,was analyzed by using statistic method.The result showed that the main meteorological factors affecting winter wheat yield in Tianjin were precipitation in 3 periods of the whole growth period,jointing to grain filling stage,before sowing and the accumulated temperature before overwintering.The precipitation in 3 periods decreased in early stage and increased during late stage. Accumulated temperature increased significantly.Regression equations for rice yield showed that the threshold of precipitation and temperature were as follows,the precipitation in the whole growth period,jointing to grain filling stage, before sowing should be 122mm,41mm,36mm respectively;the accumulated temperature before overwintering should be 511-627℃.So the probability of precipitation deficit was 22%～80% during 3 periods in last 49 years.However,the effect of rainfall on winter wheat production was decreased due to improving irrigation capacity.The probability of low temperature was 10%～50% and high temperature was 8% before overwintering for winter wheat.Accumulated temperature affected rice yield apparently.

Key words: Winter wheat, Winter wheat, Meteorological yield, Precipitation, Accumulated temperature