To estimate the subjective and objective weights of each index, the entropy weight approach is integrated with AHP in light of the current issues with building energy conservation and sustainable development. The study found that among the four indicators, the proportion of environmental sustainability is 48.19%, which has the most significant impact on the energy-saving potential and sustainable development efficiency of buildings. Among them, the weight value of the environmental load capacity index is 0.1104. On this basis, the cloud model is used for qualitative and quantitative analysis, and a comprehensive model based on four first-class indicators is established. The study found that the evaluation value of this index showed a kind of volatility, with a peak of 1 and a maximum frequency of 0.6. Overall, it displayed “generic” and “good” traits, demonstrating that people did not give enough thought to the environment’s and system’s sustainability while pursuing economic and social sustainability. In conclusion, the evaluation method chosen in this study can solve the fuzziness and randomness better in the efficiency of energy conservation and sustainable development of green buildings. This method has a significant impact on the evaluation of real green buildings.