Abstract: Based on the data of the accumulation temperature in winter from 1965 to 2005 and the data of the growing period of winter wheat,apple and pear trees from 1981 to 2005 in Xifeng station,changes of the accumulated temperature in winter and crop growing periods were analyzed,by using correlation and comparison to typical years.The results indicated that the accumulated temperature in winter increased 5.5℃ per year from 1965 to 2005.The Crops' growing period had advanced since 1994.The accumulated temperature in winter was negatively related to the growing period of winter wheat,significantly for returning green,heading and jointing stage in turn.In typical years with higher winter accumulation temperature,such as 1986,1998 and 2000,the crop growing period advanced more than in the typical years with lower winter accumulation temperature such as 1983,1984 and 1988.The total length of growing period of winter wheat advanced 21 days,and for apple tree the leaf color change stage advanced 19 days,while the middle stage of the leaf color change of pear tree advanced 20 days.

Key words: Loess Plateau, Loess Plateau, Accumulated temperature in winter, Growing period of crop