In this paper, the traverses survey was conducted to explore both the severity of urban heat island effect and cooling impacts of green areas at macro-level in Tainan Metropolis Region. Urban temperature distribution was mapped relying on data derived from the mobile survey. On the other hand, the sense of FORMOSAT-2 satellite in study area was employed to calculate the greening index, Normalize Different Vegetation Index (NDVI), of the research area by remote sensing technology. The objective of this study is to investigate the relationship between urban greening and thermal environment in Tainan metropolis region and to discuss the effectiveness that the city's greening have brought about to lessen urban temperatures and to dampen the heat island effect. This paper demonstrates the relationship existing between urban greening and thermal environment in order to explore a method to mitigate urban heat island effect and energy consumption. Knowledge on these relationships can be used by planners to recommend tree planting programs and to evaluate the need for new or revised urban design and landscaping policies for mitigating the adverse thermal effects of urban geometry, building mass and poor landscape layouts.