Phase change material (PCM) applied in the glazing roof can decrease building energy consumption and improve thermal comfort by enhancing its thermal energy storage capacity. In the present work, thermal performance of a PCM-filled double glazing roof with different thickness of phase change material was numerically investigated on two groups of extinction coefficients of solid and liquid PCM, and the effect of the semi-transparent property of the glazing roof and zenith angle on the thermal performance was also studied. The results show that the semi-transparent property and zenith angle have a big effect on the thermal performance, including temperature time lag, total transmitted energy and transmitted solar energy. With PCM thickness increasing, the temperature time lag increases. However PCM thickness effect on total transmitted energy and transmitted solar energy is different in different time, which has a big effect on total transmitted energy mainly at 0:00-14:30 and 20:00-24:00, and has a violent effect on transmitted solar energy and solar transmittance mainly at 5:00-11:00. When the extinction coefficients of PCM increase, PCM thickness effect on thermal performance parameters turns bigger except for the temperature time lag. (C) 2016 Elsevier B.V. All rights reserved.