In view of many performance problems of existing office buildings in Shanxi Province, a comprehensive and systematic performance evaluation system model was established from five aspects of site planning, building function, building structure, building equipment, and building value by using analytic hierarchy process. On the basis of this model, the fuzzy evaluation method was used to comprehensively evaluate the performance of existing office buildings in Shanxi Province, and the quantitative evaluation results were obtained. Through the analysis of the evaluation results, the key performance problems in urgent need of renovation were obtained, which provides support for the reconstruction and renewal of existing office buildings, so as to realize their sustainable transformation and utilization.