Abstract: This paper analyzed the variation of air temperature in the past 40 years based on the monthly observation of mean air temperature, maximum and minimum air temperature during 1971 ~ 2010 in Dingri meteorological station.Resultsshow that annual mean air temperature and mean air temperature in different seasons have significant increasing trend in the past 40 years over Dingri region. And, the linear trend of annual mean air temperature is 0. 394℃ /10a. The mean air temperature in winter has the largest increasing trend, followed by that in spring and autumn while the trend in summer is smallest.Similarly, the maximum and minimum air temperatures have the same increasing variation tendency as man air temperature.The linear trend of annual mean maximum and minimum air temperature is 0. 372℃ /10a and 0. 445℃ /10a respectively. The increasing amplitude of minimum air temperature is larger than maximum air temperature. Mean air temperature of different periods is basically increases rapidly from 1997, but the maximum, minimum air temperatures are increasing obviously from the 1990s.