In order to explore the role of urban green space in regulating microclimate and alleviating urban heat island, the green space of the riverside forest park in Shunyi City was taken as the object, and the hard pavement was selected as the control. The air temperature, relative humidity and wind speed of different plant communities were monitored on the spot from March to November 2022, so as to study the improvement effect of microclimate and human comfort among different plant communities. The results showed that the cooling effect was the best in spring (2.74℃), followed by that in summer (2.05℃), and the cooling effect was the most significant before 14:00 in one day. Summer humidification effect was the highest (6.88%), followed by autumn (5.62%). The effect of wind speed weakening was highest in spring (0.2 m/s), followed by that in summer (0.07 m/s), and the degree of wind speed weakening was greater in the morning. Spring, summer and autumn can improve human comfort in different degrees, and summer is the highest (1.54), followed by spring (0.54). A more comfortable environment can be provided for people all day in summer and from 12:00 to 14:00 in spring and autumn. It can be seen that the optimization and improvement of plant community plays an important role in improving the ecological benefits of urban green space and urban ecological environment. The results can provide reference for the optimization and improvement of plant community structure, operation and management, and citizen leisure travel.