Choosing Harbin as the study area, a city of typical cold climate, through the field experiment in winter (from 2013—11—01 to 2014—04—30), we measured soil temperature in the depth of 3cm, 5cm,8cm,10cm,15cm,20cm,40cm,60cm,100cm, and 140cm with four control groups (bare land, 5cm thickness of straw mulch, 10cm thickness of straw mulch, 15cm thickness of straw mulch), and air temperature and solar total radiation under different control group. The statistical analysis results show that the straw mulch can prevent heat transfer in two directions, and its dominance varies with the outer environment. Under a certain depth the soil temperature is determined by the interaction between soil thermal conductivity and straw mulching conditions. The temperature of bare land has the biggest change rate, followed by the 5cm thickness of straw mulch and the 15cm thickness of straw mulch, and the last is the 10cm thickness of straw mulch, which means that the influence of straw mulching on soil temperature does not increase monotonously with the increase of the thickness of the straw.