In order to quantitatively assess the frequency/voltage support effects of grid-following and grid-forming stations, an evaluation index system to quantify the performance of the stations is proposed, considering the power support density and energy support density. First, based on the output response characteristics of grid-following and grid-forming controlled generating units in renewable energy stations, the characteristic quantities of power, voltage, and frequency are observed over multiple time scales in terms of voltage and frequency stability. Second, the coupling relationship between the indicators is considered comprehensively, and the base weights of the indicators are derived using the best-worst method (BWM) and the criteria importance through the inter-criteria correlation (CRITIC) method. The results of both indicator types are integrated into an improved technique for order preference by similarity to ideal solution (TOPSIS) evaluation model using the game-theory-based combinatorial assignment method to achieve a graded evaluation of the station’s grid-connected performance. Finally, the DIgSILENT simulation software is used to develop a model of the power grid in southern Xinjiang for station simulation experiments. The results show that the proposed evaluation index system can effectively compare and evaluate the grid-connected performance of grid-following and grid-forming stations from various aspects.