Reflective and insulative composite coatings are a new energy-saving material with high solar reflectance and extremely low thermal conductivity for buildings. The optimization and impact of high solar reflectance and low thermal conductivity on the insulating capacity of walls remain uncertain. This work investigates the dynamic thermal performance and energy efficiency of a reflective and insulative composite coating in regions with hot summer and warm winter. A simplified thermal resistance-heat capacitance model of an exterior building wall is established to predict thermal performance. The dynamic temperature and heat flow of the wall are predicted to reduce heat loss through the interior surface of the wall and compared to the conventional coating. The specific impact of the thermal conductivity and solar reflectance of the coating on the heat loss is further investigated to minimize heat loss of the wall. This research shows that the composite coating shows better performance on adjusting outdoor climate change than the other coating. Compared with cement, it reduces the maximum temperature of the exterior surface of the wall by 7.45 ℃, and the heat loss through the interior surface of the wall by 38%. The heat loss is reduced with the increase of solar reflectance and the reduction of thermal conductivity. The results can provide a useful reference and guidance for the application of reflective and insulative composite coating on building exterior wall to promote their energy-saving use on building envelopes.