To quantify the effect of PCM on the indoor thermal environment of sports facilities, this study combined experimental and numerical simulation methods. The experiment used a 1:10 scale model of a university gymnasium as the experimental object. Using a three-variable orthogonal design (PCM fill ratios of 10%, 20%, and 30%. Installation locations: built-in wall, spray-coated roof, and embedded floor). These fill ratios align with typical PCM dosage ranges in building envelope research, while phase change temperatures (24°C, 27°C, and 30°C) reflect optimal indoor comfort ranges for sports activities. The results showed that under high summer temperatures, for every 10% increase in PCM fill ratio, the indoor temperature fluctuation decreased by approximately 0.3°C. The PCM with a phase change temperature of 27°C had the fastest activation. Numerical simulations were conducted using COMSOL Multiphysics 6.0, using a 1:1 modelling platform. Simulation errors were kept within 5%. The results show that the 30% fill ratio solution for 27°C wall installations offers the best overall performance, with a maximum daily temperature difference of only 2.1°C in summer (a 41.7% reduction compared to the no-PCM solution), an average annual energy saving of approximately 13.8%, and a pay-back period of 3.5 years. This research provides data support for optimizing PCM application parameters in sports facilities.