Abstract: In this paper, the two solar greenhouses with the same sizes of a vegetable planting base located in Beijing were researched, and one was taken as test greenhouse, the other reference greenhouse. The phase change materials (PCMs) was applied on the inner surface of the test greenhouse’s north wall in order to enhance the wall’s ability to collect and store solar energy and increase the utilization rate of solar energy, and then improve the indoor thermal environment of the greenhouse. According to the measured data from Dec. 21, 2010 to Jan. 18, 2011, the results showed that the thermal performance of the test greenhouse with 40 mm thickness PCMs was better than that of the reference greenhouse with conventional brick materials. During the opening of the heat preservation quilt in the daytime, the inner surface average temperature of the north wall of the test greenhouse was about 1-2.7℃ higher than that of the reference greenhouse, the soil average temperature of the plow layer and the average indoor ambient temperature of the test greenhouse were about 0.5℃and 0.2-2.1℃ higher than that of the reference greenhouse, respectively. During the closing of the heat preservation quilt at night, the inner surface average temperature of the north wall, the soil average temperature of the plow layer and the average indoor ambient temperature of the test greenhouse were about 2.1-4.3℃, 0.5-1.4℃ and 1.6-2.1℃ higher than that of the reference greenhouse, respectively. So the PCMs can improve the thermal environment for crop growth and increase the utilization rate of solar energy in solar greenhouse.