With the economic rapid development in Asian developing countries, megalopolis such as Shanghai and Bangkok have been grown rapidly and have significant effects on an urban thermal environment and air pollution. It is an urgent work to find a way to improve the urban environment in the developing countries. In this study, a method has been developed to establish a digital database of land use based on a land use map because there are few GIS data in the developing covmtries. By this method, five megalopolises, New York, London, Tokyo, Shanghai, Bangkok have been selected as a case study. Based on the evaluation, a comparison between those five megalopolises has been investigated in order to determine the characteristics of thermal environment in those five megalopolises. The results showed the average air temperatures are affected mainly by built areas and water surface areas. A large river, such as that in New York has a good effect on mitigating the urban thermal environment. A good arrangement of green spaces like London can also mitigate air temperature. The increase of the urban area in the developing countries will significantly affect the thermal environment in future. Therefore, a good plan with the consideration of green and water spaces is needed in order to conserve the environment.
