An introduction is made to two different instruments for measuring ground surface temperature. Based on the ground surface temperature data observed by the two instruments in the Xilinhaote National Climate Observatory from January 2007 to February 2008， the differences between the two observed data in different weather conditions are analyzed and compared. The results show that the difference was mainly influenced by solar radiation and the conditions of the underlying surface. At high temperature in Summer, the difference, affected greatly by solar radiation, was considerable large in daytime， and relatively small in night. At low temperature in winter, the difference was small and the data were of good comparability. The results also show that the two sets of measurements tend to be close when it rains. However, the difference increases with the depth of the snow.