Comparative experiments of indoor thermal environment were undertaken, with night ventilation, in lightweight buildings with Phase Change Material (PCM) and without PCM. And the lightweight building fabric with PCM is made of selfmaking compound organic PCM and attached with EPS. Analysing the influence of PCM dosage, phase change temperature and PCM wall structure on the PCM wall performance of heat storage and release and indoor thermal environment, it was shown that the thermal inertia of enclosure could be advanced with PCM and indoor thermal comfort could be improved as well. With the night ventilation, the heat accumulated in daytime could be released outdoor. And the maximum indoor temperature decreased 11 ℃ in PCM building compared with that in common building, which met the third grade requirement from spatial and indoor environmental parametric requirements for camping (GJB 4306-2002) and held remarkable energy efficient potential. With regard to the influencing factors, dosage and phase change temperature were the key factors. And with different phase change temperatures, the temperature difference could be increased from 3 ℃ to 11 ℃ when PCM dosage doubles. Optimization design of Phase change temperature and dosage could improve the PCM performance effectively.