Abstract: Based on observation data of leaf temperature in secondary forest gap in rain season(July 1999)of Xishuangbanna,temporal and spatial variations of colonists′ canopy surface temperature were discussed.The results indicated that:influenced by the solar radiation and thermal effect of forest edge,the maximum thermal active area of colonists′ canopy surface was different in different period of time.The leaf temperature difference between observation sites and the center of the gap were significant,especially at the noon.When the air temperature was 25.8 ℃,the leaf temperature was equal to air temperature,however,the emergent time of balance temperature was different in various azimuth and south edge of gap kept balance status in the whole day,due to effects of sunlight and trees at the edge of gap.Influenced by overcast and shade effect of trees,leaf temperature was equal to air temperature on observation sites after 16∶00 p.m.Whereas in clear day and no shade effect,leaf temperature was higher than air temperature,with the difference ranging betwwen 0 ℃ to 3 ℃ .At the time 15∶00 p.m.when the rain stopped and the sun appeared,leaf temperature was lower than air temperature because of leaf surface vaporizing water and consuming heat.This maximum displayed dynamic displacement may have a profound effect on species invading,colonizing and reproducing,further on species composing within the gap.