This study aims to find the impact of different ground surfaces on thermal environments in outdoor activity space. Field measurements were conducted in a university campus located in the hot summer-cold winter climate zone. Five typical outdoor ground surfaces were selected: light-colored marble brick, plastic track, bluestone slate under the shade, lawn under the shade, and unobstructed lawn. Thermal environment parameters, including air temperature, relative humidity, solar radiation, surface temperature, mean radiant temperature (Tmrt) and the physiological equivalent temperature (PET) were measured and calculated for summer and winter, respectively. It is confirmed that the property of the ground surface had a significant effect on surface temperature and Tmrt in winter and had a significant effect on relative humidity and PET in summer. The use of ground surfaces with low reflectivity which could increase the surface temperature by 4.5 °C in winter while reduce the heat stress (PET) by 3.7 °C in summer, should be encouraged in outdoor activity space.