Abstract: Wide plastic film mulch has demonstrated obvious positive effect on soil temperature. A field experiment was conducted in Kuitun, Xinjiang, to investigate soil temperature dynamics for four scenarios: three within the mulch (clearance, middle and side), and one with the mulch removed. The variation of upper layer soil temperatures (5 cm deep) can be fitted as a sine function, and the daily variation can be characterized by three measurements at 8:00,16:00 and 20：00. For the upper layer soil in the planting season, the maximum temperature, maximum temperature fluctuation, and maximum average temperature all occurred under the middle of the mulch, which was followed in turn by the side and clearance of the mulch, and with the mulch removed. Soil temperatures of clearance, middle and side at different depths have their variation both in a day and in seasons. For different soil depths, the amplitude of temperature daily variation can be approximated as an exponential function of the depth.