 The paper analyzes the effect of urban heat island on Hong Kong using Landsat TM and Astrodata in 2005, applying two algorithms to retrieve land surface temperature, LST, distribution and exploring the impacts of green and built-up lands on urban heat island by calculating ecological evaluation index. The results indicate that three suburban areas are mainly affected by urban heat island, with negative correlation between LST and NDVI suggesting that green land can weaken the effect, while positive correlation between LST and NDVI means built-up land can strengthen it. However, in-situ measurements of LST are needed to refine the method in future studies. This article was authored by Lin Liu and Yuan Zhizhong.