China’s provinces have explored paths to improve power supply reliability (PSR) to cope with the high penetration of renewable energy connected to the grid. For this purpose, it is essential to quantitatively evaluate the PSR situation in each province and identify the key impact indexes. This study firstly comprehensively considers the influence of power supply, grid, customer, market, and energy storage sides and selects power supply and demand, renewable energy development, power transmission, and power market indexes to construct a provincial PSR evaluation index system. Secondly, the weights obtained from the Analytic Hierarchy Process (AHP), entropy, and Criteria Importance Though Intercrieria Correlation (CRITIC) method are coupled using the game theory equilibrium idea to derive the integrated weight values. Finally, a three-dimensional provincial PSR evaluation with spatial (31 provinces), index (4 primary indexes, 26 secondary indexes), and temporal (2016-2020) dimensions is combined with the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method, and a differentiated improvement strategy is proposed. The results show that the electricity market is the most important, followed by electricity transmission. Shanxi and Jiangsu had the highest PSR in 2020. Gansu, Ningxia, Shanxi, Jiangsu, and Fujian significantly improved PSR in 2016–2020. A declining trend in the reliability of power supply and demand in Northwest China, Central China, and the Eastern coastal region in 2018–2020. Electricity market reliability in 2016–2020 is basically positive growth, peaking regulation auxiliary service market running time and inter-provincial trading power two indexes are the most important.