In response to the rapid development of the grid forming energy storage (GFES) market and the inconsistency in product quality, this paper proposes a performance evaluation method for GFES based on the entropy-weight TOPSIS (technique for order preference by similarity to an ideal solution) model. A GFES evaluation system platform that integrates product testing and multi-dimensional evaluation is designed and developed. First, four key indicators are selected to construct the performance evaluation system for GFES, including inertia support, primary frequency regulation, low-voltage ride through, and energy conversion. Corresponding testing methods and quantitative indicators are provided. Then, the hardware environment and software platform of the testing and evaluation system are introduced in detail, and the detection efficiency is improved by simplifying traditional manual testing methods. Finally, real waveform from GFES are used as sample data to experimentally verify the evaluation system platform, and a quantitative comparative analysis is conducted across different GFES types and power levels, demonstrating the accuracy of the evaluation system and the effectiveness of the evaluation model. The system provides strong support for the advancement and adoption of GFES technologies.