For quantitative analysis of soil heat transfer and taking measures to increase temperature, the 2-D unsteady simulation model of soil temperature was built by using the finite difference method. After validating the correctness of the model by the data measured in the solar greenhouse of northwest China, the soil temperature simulated agreed well with the measured data. The mean absolute error was 1.3℃, the mean relative error was 9.5%, and the root mean square error was 1.5℃.