Building anthropogenic heat emission is one of the key factors contributing to both building thermal environment and urban heat island, which can potentially lead to increasement of building energy consumption and carbon emission. Mitigating this heat through green belts is an effective solution to achieving low carbon development in buildings. Therefore, this study analyzed the impact of the location and type of green belts around buildings on the thermal environment around buildings. A co-benefit assessment model was developed to quantify green belt design parameters based on the identification of optimal green belt types and locations. Results showed the building thermal environment was significantly influenced by anthropogenic heat emission, leading to a maximum increase of 3.4°C in air temperature. Compared with buildings without green belts, the optimal green belt design (i.e. lawns, shrubs and trees configuration) could decrease the temperature around the building by 1.85°C, while the cooling efficiency reached 47.20%. The optimal lawn area distance was determined to be 0.5 S (S is the building’s footprint), the optimal shrub length was found at 0.6 L to 0.8 L (L is the length of the building), while the optimal tree spacing distance was determined to be 3.5 m to 4.0 m in this study.