By choosing three national weather stations soil temperature data at the depth of 0,5, 10, 15, 20, 40, 80 cm in May-September of 1965-2000, we studied the change character of soil temperature in Inner Mongolia steppe grassland region. Soil temperature at 0-40 cm is highest in July,and soil temperature at 80 cm is highest in August. Soil temperature over the past 35 years during the growing season reveals a increasing trend, with the rates of 0.032℃/a at 0 cm, 0.035℃/a at 5 cm, 0.039℃/a at 10 cm, 0.035℃/a at 15 cm, 0.036℃/a at 20 cm, 0.023℃/a at 40 cm, 0.035℃/a at 80 cm, respectively. The temporal change can be divided into two stages : stable period and significant warming period, and soil temperature for all layers began to rise sharply since the mid 1990s. Soil temperature change is closely related with precipitation and air temperature, and these two indicators are important climate factors that influence soil heat exchange.