The effects of three-dimensional green biomass on cooling and humidification of 48 typical plant communities among green spaces in urban and suburban parks of Huaihua city during 11:00-15:00 in summer were analyzed. The results show that the height of plant community, the number of layers, the total three-dimensional green biomass density, the three-dimensional green biomass density of trees and the three-dimensional green biomass density of shrubs are significantly positively correlated with the cooling and humidification rate, while the three-dimensional green biomass density of ground cover plants is significantly negatively correlated with the cooling and humidification rate. When the three-dimensional green biomass density of trees is close to 9.9 m3/m2, the cooling rate reaches 22.23%. When the height of plant community is close to 18.0 m, the cooling rate reaches 20.44%. When the three-dimensional green biomass density of trees is close to 11.08 m3/m2, the humidification rate reaches 65.64%. When the height of plant community is close to 22.3 m, the humidification rate reaches 65.10%. Compared with suburban parks, urban parks have lower plant community height, less layers and smaller total three-dimensional green biomass density, thus lower average daily cooling rate and humidification rate.