Green roof contributes to high total thermal resistance of roof serving as additional equivalent thermal resistance ，which effectively reduces the heat gain from roof and lowers the indoor air temperature. However，current studies showed that the relationship of indoor temperature and thermal performance was coupling and the performance of the green roof are different with the change of the indoor temperature. Surface temperature and heat flux changes of green roof，reference roof and equivalent insulating roof were analyzed respectively when the indoor temperature changed using both experiment and numerical simulation. The results showed that the indoor temperature had significant impact on the insulation performance of green roof and the equivalent thermal resistance had positive correlationwith the indoor temperature. The insultation performance of green roof reduces heat gain in passive building.Key words:green roof;equivalent thermal resistance; numerical simulation.