According to population growth, urban sprawl, as well as global warming, attention to the impact of design on thermal comfort in open spaces is important. Thus, it is essential to climate studies and understanding environmental features, as well as results usage in improving designs. The aim of this research is to use optimal climate knowledge to improve the quality of urban spaces; so with suitable use of natural resources can be achieved in a sustainable urban environment and responsive to the needs of human. With regard to the simulation and analysis by ENVI-met software, the result of this paper showed that, by choosing the suitable species and number of trees on outdoor, Ta and the MRT in the summer were reduced by 0.29 ˚C and 20.04 ˚C respectively and the RH increased by 3.51%. Overall, PET improved from 34.92 to 26.16 ˚C and PMV decreased from 2.31 to 0.86 in the summer which means that they are reached around comfort zones.