The assessment of effect about economic incentive policy of renewable energy building is affected by many factors. The single index evaluation is not only short of scientific basis, but also has great limitations. The research analyses the principles of evaluation index system from the perspective of low-carbon and establishes a multi-index comprehensive evaluation system considering the external characteristics of renewable energy building. The system mainly includes the economic, environmental and social benefits. According to this system, AHP and attribute mathematics theory are used to evaluate the effect of incentive policy.