| The 3S technology and geographic information system platform is employed in this essay to analyze thermal spatial configuration of Hefei city, the study area covers 716km~2 of four urban districts. All spatial analysis was made by ArcGIS. The dynamic trend of thermal environment in the study area from 2003 to 2007 was described, the causes of the differences in thermal field distribution in the period were proposed based on landscape ecological principles, and the relationship between heat island effect and vegetation distribution was built too. This paper will provide a scientific basis for alleviating of heat island effect and microclimate improving in urban area. The results as the follows:(1) From ground brightness temperature distribution of Hefei in 2003, the second ring road was distinguished as the dividing line of thermal field distribution.The heat field was concentrated in center of downtown within the Second Ring road and formed heat island, and radiated to the surrounding regions. The central business district, old town, residential areas, as well as old industrial areas and new industrial zone is the distribution area of high temperature and Secondary high temperature, in which bright temperature in Southwest is higher than that in Northwest. In general the distribution pattern of the heat island in both 2003 and 2007 is similarly, but the heat island appearance has been eased, reflecting that in the distribution of heat island within the second ring road in 2007 is not concentrated as that in 2003, the area with higher and second higher bright temperature decreased, the distribution pattern of heat island transformed from block-shape and line-shape in 2003 to point-shape in 2007, but the center of heat island expanded to outside the Second Ring in 2007, there were more small areas of heat field in outside the Second Ring.(2) Based on the comparison of the heat island patterns combined with land use maps between 2003 and 2007, we can made a conclusion that urban green coverage was improved in 2007 compared with 2003 since green land increased in all studied districts in particular the urban forest area increased. Which had higher contribution for improving of thermal environment. Meanwhile author concluded that there is significantly relationship between greening coverage and the heat island effect , we found that the higher greening coverage in a region, the higher percentage of low-temperature field is, then thermal environment is better, So increasing the urban greening is an effective way to alleviate the heat island effect.(3) Based on analysis of the landscape index of urban forest patch, both of the fragmentation and the separation of urban forest patches in 2007 was lower than that of in 2003, aggregation of urban forest landscape patch in 2007 was higher,the ability adjusting the temperature of the ground increased, thermal environment in 2007 was improved significantly compared with that in 2003.(4) With quantitative analysis, a negative correlation between the heat island effect and leaf area index (LAI) for different types of vegetation was suggested by author,as LAI of urban forests elevates 0.1 every time, the temperature drop 0.297℃; LAI of generally green land LAI elevates 0.1 every time, the temperature drop 0.188℃.So regulate climate ability of urban forest is higher than general green land.⑸As a cold source green land has effect significantly on thermal field of its surrounding region, in which a temperature gradient could be measured, and the bright temperature will increase with distance to green land increase, When it increase to a limit distance where bright temperature back to as higher as heat field , the scope could be called as thermal effect range of green field.This rage was changing with area changing of green land. The greater the area of green patch, the more impact on its surrounding temperature. Its relationship could be described using the follow regulation.:y = 0.0004x +142.8 R~2 = 0.7883...
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