In dry hot season,microclimatic measurements were conducted in the process of the different growth phases (gap phase, building phase and mature phase) of tropical forest in Xishuangbanna. The microclimatic characteristics of different growth phases of tropical forest were discussed in this paper.The results indicated that in dry hot season, there was a distinct microclimatic difference between forest in different growth phases and open field. There had a significant effect on reducing air temperature and improving moisture in the interior forest.Due to the differences of community structure, canopy density and thermal character in different growth phases of tropical forest,the effect of reducing air temperature and improving moisture was different and state of microclimatic factors was also different with temporal variation, which would influence on growth and development of vegetation in different growth phases of forest. This study presents a research basis for discussing mechanism of regeneration,biodiversity of forest community and improving the utilization ratio of all kinds of environmental factors by forest.