Microclimatic measurements were conducted near to the edge of secondary forest canopy gap in Xishuangbanna,Yunnan province in Jan.1999.The daytime spatial temperal characteristics of boles surface temperature at the edge of canopy gap and the interior of secondary forest and the thermal characteristics were discussed.Spatial temperal changes in surface temperature and its defferences between the edge of canopy gap and the interior of forest were also analyzed.The findings show that there are four thermal active surfaces on the vicinage of canopy gap,they are canopy surfaces,soil surface on the interior of forest,woody wall surface of edge and soil surface on the gap.The woody wall surface of edge on the East and North are a key thermal active surface of the canopy gap and the thermal variation were controlled by the thermal characteristics of four active surfaces and the interaction.The results provide a research basis for understanding microclimatic formation of canopy gap,and for studying impacts of forest fragmentation on biodiversity.