Macao city located in the Pearl River delta, China, was chosen to study the effect of urban heat island and its time-series analysis of land surface temperature (LST) in spatial expansion. The LST was analyzed by a temperature separation method based on statistical results. In the case of urban area, it was composed by three parts: downtown and old built-up areas with high-density buildings and dwellings, new built-up areas and developing site. The trend of city development was studied that the developing site would become to be new built-up areas and the formerly new built-up areas would become to be the downtown and old built-up areas. These three parts stand for different stages of a city.