According to the observing data of soil temperature in root layer under three thickness of roof greening coiled materials, soil temperature under natural conditions, and air temperature, we studied the variation characteristics of soil temperature in root layer under different roof greening coiled materials by the methods of comparative analysis and linear regression. The results showed that the annual variation of soil temperature in root layer was in accord with that of air temperature. The roof coiled material had the function of insulation, and the insulation effect on soil temperature of root layer was enhanced with the increase of film thickness. The diurnal change amplitude of temperature decreased with the increase of film thickness, which could be fitted as an exponential function. Moreover, there was an extremely significant linear relationship between air temperature and soil temperature in root layer under roof greening coiled materials.