Abstract: Based on the daily meteorological data of 113 weather stations in the main planted areas of winter wheat from 1961 to 2008,the characteristic of agricultural climate resources during the growing period of winter wheat was analyzed by using Mann-Kendall rank analysis and linear trend estimate method.The results indicated that the accumulated temperature higher than 0℃ during the growing period of winter wheat significantly increased,and it had an abrupt change in the beginning of 1990s.The precipitation and reference evapotranspiration had little change during the growing period of winter wheat over last 50 years,however,the fluctuation of precipitation and reference evapotranspiration inter-annual was intensified.The reference evapotranspiration decreased in 1980s and increased slightly after 1990s.The first frost date was delayed and the last frost date was ahead of time,which caused decrease of the frost days over the last 50 years.The first frost date delayed significantly and the last frost date became earlier since the beginning of 2000s.

Key words: Winter wheat, Winter wheat, Agricultural climate resources, Changing characteristic