Fourteen plant communities with different structural characteristics in Beijing Botanical Garden were selected for the test of temperature and humidity by JL-17 temperature and humidity recorder.The correlations between temperature decreasing and humidity increasing effect of plant communities and their crown density,average crown width,LAI were studied.The results showed that different plant communities had various temperature-decreasing and humidity-increasing function.The plant communities consisting of Prunus persica Batsch.var.duplex,Fraxinus pennsylvanica,Liriodendron chinense×tulipifera,and Eucommia ulmoides had stronger capacity,while the plant communities consisting of Salix matsudana f.pendula,Catalpa bungei and Paulownia tomentosa were a little worse.Simultaneously the analysis showed that temperature-decreasing was very significantly and positively correlated with the crown density,and humidity-increasing was positively correlated with it,but not significantly.Meanwhile temperature-decreasing was also significantly and positively correlated with the average crown width,but humidity-increasing was less positively correlated with the average crown width.LAI had a significant impact on temperature-decreasing but less impact on humidity-increasing.In addition,other structural characteristics affecting temperature-decreasing and humidity-increasing effects of plant communities should be further studied.