An advanced and efficient evaluation system is the driving force for the continuous improvement and perfection of power grid operation， and different backgrounds of electricity system reform play an important role in guiding and determining the establishment of evaluation system. In addition， fully considering the effects of power reforms is also one of the key factors to guarantee the successful establishment and implementation of the grid assessment system. This paper chose the representative CEER Benchmarking Report on the Electricity Supply Quality and America Grid Modernization Index （GMI） for detailed research. First of all， starting from the reform course and marketization level， it combed the development of electric power system reforms in the United States and Britain. Secondly， this paper researched the evaluation systems of the two benchmarking grid and carried out a contrastive analysis based on the background of their different reforms. Finally， according to the international experience， this paper presented the enlightenment and revelation for the establishment and improvement of grid evaluation system in China considering the new-round electricity reform.