To promote and develop green buildings,a standardized,applicable and easily operable index system for the assessment of such buildings was established on the basis of life cycle cost effectiveness.From the perspectives of environment-friendly materials,water resource environment,energy and environment,quality of indoor and outdoor environment,operation and management,and economical efficiency of life cycle,a modified index system was built,AHP was applied to obtain weights of indexes,evaluation methods of the grey system were used to evaluate green buildings,case study was adopted to verify the practicability and scientificity of the method.The results showed that Grey Clustering Method was an objective and reliable tool to evaluate green buildings,the calculation was simple,practical and easily operable,and moreover,the assessment process could be optimized by computer programming to improve its efficiency and precision.