To analyze the effect of underlying surfaces on local thermal climate, this paper took the international low-carbon city of Shenzhen as an example, and the effects of different underlying surfaces on the urban heat island (UHI) and outdoor thermal comfort were discussed by using multipurpose regional thermal climate prediction model. The results showed that the maximum urban heat island intensity(UHII) reflected the temperature difference between urban and suburban of the hottest cases while the average local UHII reflected the average difference of the whole day. And the average local UHII of night was higher than the average local UHII of daytime. Besides, the cooling effects of water and trees were better compared with other natural underlying surfaces, while appropriate increase of grass coverage could more effectively improve the outdoor thermal comfort.