Abstract: Under the environment of global warming, it is important to study the variations of surface temperature and temperature in the different soil layers for the industrial and agricultural production. Based on the ground temperature and the maximum and minimum temperatures on 0 cm soil layer from 1961 to 2010, the ground temperature in 40 cm and 80 cm soil layers from 1961 to 2010, the ground temperature in 160 cm and 320 cm soil layers from 1980 to 2010, the variation trends of temperatures on the ground and in the different soil layers were analyzed with a least square method. The results indicate that temperatures on the ground and in the different soil layers are all in increasing trends. The significant warming appears in winter, while the decreasing trend of temperature is in summer. The increasing trend of the minimum temperature on the ground is the most significant and its ratio is 0.47 ℃/decade, and the maximum ratio is 0.74℃/ decade in winter, while the increasing trend of the maximum temperature on the ground is not significant and its ratio is 0.15 ℃/ decade. The increasing trend of temperature on 0 cm soil layer is 0.27 ℃/ decade; the decreasing and increasing trends of temperature is -0.04 ℃/ decade in summer and 0.51℃/ decade in winter. The variation trends of temperature in 40 cm and 80 cm soil layers are consistent, while their warming amplitudes are lower than that of temperatures on the ground, and in160 cm and 320 cm soil layers.

Key words: Ground temperature, Least square method, Tendency rate, Ground temperature, Least square method, Tendency rate