Abstract: Soil temperature affects strongly the crop growth, soil watersalt transport, biological activity and quantity, and soil carbon balance. In order to study the differences of biological crust and bare sand soil temperature in Mu Us Sand Land, some sunny days were selected to conduct the experiments in Gechou Ditch in the Mu Us Sand Land located in Shenmu County, north Shaanxi Province during the period from September to November 2010. The results are as follows: (1) The change trend of soil temperature at the same depth was the same in both the plots of biological soil crust and bare sand; From 6:00 to 21:00（every 3 hours）,the soil temperature curves were “\”, micro“(”， obvious “(”, “/”, micro “)” and “\”; (2) Biological crust cover decreased significantly the topsoil temperature (P<0.01); (3) The change range of topsoil temperature in both the biological crust and bare sand plots was the highest, and it was decreased with the increase of soil depth. The effect of biological crust on soil temperature at the same depth was more significant. From the perspective of vertical profile, biological crust decreased the soil temperature and its change range; (4) Biological crust enhanced the sensitivity of soil temperature at depth of 0-25 cm to air temperature. The study results showed that the change of soil temperature was affected by many factors, and the previous achievement that the effect of biological crust on soil temperature was judged with the biological crust color was not reliable. The effect of biological crust on soil temperature is probably caused by that biological crust changes the topsoil structure and moisture conditions. Soil moisture evaporation, soil chemical properties, etc., especially the temperature effect of biological crust on these processes, should be paid more attention to in the future.

Key words: biological soil crust, soil temperature, soil moisture content, daily amplitude, Mu Us Sand Land, north Shaanxi Province