Abstract: The variation and mutation of temperature at inter annual and seasonal scales and their impacts on agriculture were analyzed,by using of linear trend analysis,moving average methods and Mann-Kendall,based on daily and monthly average temperature data of 3 stations in the upper reaches of Hanjiang river in Southern Shaanxi from 1960 to 2010.The results showed that the annual average temperature and annual average minimum temperature increased generally at the rate of 0.107℃/10y(P<0.01)and 0.16℃/10y(P<0.01)respectively,but annual average maximum temperature did not increased obviously.The mutation point for annual average temperature,annual average minimum temperature,and annual average maximum temperature were detected in 2001,2000 and 2001 respectively.The seasonal change showed that greater in winter(P＜0.01),and it had large contribution to climate warming.Temperature decreased a little in summer,but increased extreme significantly in spring and significantly in autumn.Late spring coldness delayed,with high intensity and high frequency.The frequency of autumn chilling decreased with longer duration greater intensity.Therefore,late spring coldness and autumn disasters caused a serious damage on crop production,including rice,maize and wheat.It was help for adapting to climate change and ensuring food security to understand climate change and its mechanism in upper Hanjiang river.

Key words: Upper reaches of Hanjiang river in Southern Shaanxi, Maximum temperature, Minimum temperature, Late spring coldness, Autumn chilling