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Adaptive building envelopes with advanced optical materials have received much attention as they can actively regulate solar heat gain. In present work, an adaptive building roof (ABR) combining variable transparency shape-stabilized PCM (VTSS-PCM) was proposed. A numerical model was developed firstly for dealing with time-space effect of radiation properties of VTSS-PCM and validated by experiments. The difference in performance between ABR and the common insulation roof was simulated. Then, a global sensitivity analysis based on the Monte-Carlo method was conducted to determine key parameters among 22 system parameters. Finally, the influences of key parameters on the performance of ABR were studied in detail. The results show that the ABR can reduce the heat gain by 35.25 % compared with the common insulation roof. The thickness of VTSS-PCM, the extinction coefficient of VTSS-PCM in the transparent state, and the albedo of reflective film are three key parameters. The thickness of the VTSS-PCM layer and the extinction coefficient of VTSS-PCM in the transparent state have positive correlations with the heat gain, whereas the albedo of the reflective film has a negative correlation with the heat gain. The time-space effect of radiation properties of VTSS-PCM during the phase change causes the solar absorptance of ABR to be unstable. This research guides the modeling of VTSS-PCM and facilitates the application of ABR. [ABSTRACT FROM AUTHOR]