There is a problem of disordered grid-connection mode of roof photovoltaics. Thus an evaluation index system containing three dimensions of stability, economy and low carbon is constructed, and a weight evaluation model based on fuzzy analytic hierarchy process (FAHP) and improvement CRITIC method is designed. Because of the bias of the traditional single weighting method, FAHP is used to give subjective weighting to the first level index to highlight the purpose of evaluation. At the same time, considering the positive and negative correlation coefficients and the discrete degree of data, the CRITIC algorithm optimized by the entropy weight method is adopted to objectively weigh the second-level indicators to enhance the scientific weight, and then the final weight is obtained through combination weight. Finally, two sets of simulation examples are set for a rooftop photovoltaic system. Five weighting methods are used to assign weights to the indicators, and the topsis algorithm is used to perform comprehensive scoring. After comparative analysis, the rationality of including the income from carbon trading and auxiliary services into the economic indicators is demonstrated. The effectiveness of the proposed index system and evaluation method is shown.