With the rapid development of global industrialization and urbanization and the aggravation of climate warming, the urban heat island (UHI) effect has become an important environmental problem affecting human survival and development. In 2020, China clearly set a “dual carbon” target. Because the location and layout of urban green space are related to the function of carbon sink, the study of the relationship between the construction of urban green spaces and the heat island effect is of great significance. This study was based on Landsat 8 remote sensing images of the Tongzhou District, Beijing, from 2013 to 2019 and examined the effect of urban green space construction and the heat island effect in the Tongzhou District at three scales: the macro level of the overall construction environment, the meso level of the urban area, and the micro level of the individual park. The results show that: (1) when the vegetation coverage was increased by 10% in the Tongzhou District, the temperature decreased by 0.58–0.68 ℃; (2) the change in the heat island in the Tongzhou District had a circular layered structure, the degree of mitigation produced by green space in different circles differed, and the effect of urban and rural transition areas was obvious; and (3) parks have different effects on the temperature drop inside and outside the park. The cooling benefit was higher when the area of an individual park was 105 ha or less, and a park including both forest and wetland had better cooling ability. This study clarifies the direction of urban space cooling and carbon control at different levels and proposes a multi-scale planning decision–making process for urban green space based on temperature orientation, thereby providing a theoretical reference for macro policy, standards, planning, and park design of urban green spaces.