As a public building for exercises and entertainments, gymnasiums play an important role in people's daily life. In regions with hot-humid climate, thermal sensation in gymnasiums is directly related to the human health as well as energy consumption. However, little can be found in the systematic evaluation system reported for thermal sensation of athletes in gymnasium in hot-humid climate regions; therefore, there is a need to develop a thermal sensation model for evaluating thermal sensation of athletes partaking sports in these environments. In this study, a field survey on thermal sensation of players in a basketball game was carried out in a naturally ventilated gymnasium in Guangzhou, China. The results showed that the human physiology and thermal sensation of subjects were highly different during active sport state. Moreover, the thermal sensation vote was increased with a rise in the air temperature, the mean radiant temperature and humidity ratio, while thermal sensation vote was reduced with an increase in the air velocity. The metabolic rate, systolic blood pressure and skin temperature were shown to have a positive correlation with the thermal sensation vote. According to the analysis, a predictive thermal sensation model, which has been developed by this study to estimate the thermal sensation under high-intensive sport activities in gymnasiums in regions with a high temperature and high humidity, was evaluated and validated.