Abstract: The blue-green space, consisting of water and vegetation, can effectively mitigate the negative influence produced by urban heat island, which will help improve the urban thermal environment and promote the sustainable development. In this study，Landsat images collected from 2004, 2010 and 2014 were used to retrieve land surface temperature to characterize the thermal environment. The cooling island intensity and index were constructed to explore the spatial-temporal characteristics of the cooling island produced by blue-green space. The profile analysis and statistic method were employed to study the impact of the total area of blue green space, land use and land cover changes and social economy factors on the cooling island. The results showed that: from 2004 to 2014, the area of cooling island zone had decreased by 24.04%, which were mainly located at the north and east part in Suzhou. However, the cooling island intensity of the blue-green space were 6.3℃,7.1℃, and 9.6℃ in 2004, 2010 and 2014, respectively, which showed an increasing trend. However, when taking the area changes of blue green space into account, the cooling effect produced by blue and green space has decreased because of urbanization. The cooling effect of blue space (10.5℃) consisting of water was much higher than that of green space (4.8℃) which was consisted of vegetation, and the cooling effect of flowing river was stronger than still lakes. The changes of land use and land cover could make big differences on the spatial pattern of the cooling island. The loss of paddy land was the dominant factor for the expansion of urban area, resulting in the loss of cooling island zone at the same time. However, the total area of lakes in Suzhou has increased a little during 2004 to 2010, which reflected the choice of protection for different blue and green spaces by decision makers.