The important point among Green building index systems is to improve the utilization of renewable energy. The usage of renewable energy can reduce carbon emissions and primary energy consumption. It has great significance to the strategy implementation of environmental improvement and of energy conservation and emission reduction. Due to the lack of legal basis of renewable energy applications in building, incentive policies and some fiscal subsidy would play an important role. As the existence of external problems, the market for renewable energy building development is affected greatly by the incremental cost, market acceptance and policy influence. Based on the principle of external economy, the method of using compensation mechanism to resolve external problems and to compensate the losses of carbon emissions is put forward through the analysis of the model of externality of renewable energy building, and further the theoretical proof of the feasibility implementation is given. The study has some guiding significance and theoretical value to promote the policy implementation of renewable energy building.