Abstract: Due to the inconsistency between energy consumption centers and energy production distribution patterns in China, it is of great significance to build UHV power transmission projects that are characterized with long distance, large capacity and low loss. The performance evaluation of an UHV power transmission project is the key to judging whether the project can achieve the expected goals and meet the requirements of project construction. A comprehensive performance evaluation index system is constructed for UHV power transmission projects from four dimensions of operation, finance, environment and society, and a comprehensive performance evaluation model is proposed for UHV power transmission projects based on Bayesian best-worst method and improved matter-element extension model. The former combines Bayesian theory and the best-worst model to determine the weight of each criteria, while the latter improves the traditional matter-element extension model to achieve the grade ranking of the comprehensive performance for UHV power transmission projects. A case study is made on a ±800kV UHVDC power transmission project, and the result shows that the overall performance of the project falls into ‘Medium’ grade. The case study shows that the proposed model is effective and scientific for comprehensive performance evaluation of UHV power transmission projects.