The thermal radiation field on building surfaces is an important part of the urban thermal radiation field and has a great impact on the urban thermal environment. This paper analyses the formation mechanism of the radiation field on building surfaces, and puts forward the evaluation indexes of the thermal effect of the radiation field. The single factor influence analysis of the radiation field is carried out from four aspects: material type, roughness, short-wave reflectivity and long-wave emissivity, and it is found that the reflectivity and emissivity have significant effects. Based on this, a comprehensive test method is used to conduct a multi-factor analysis of the coupling effect of reflectivity and emissivity. The research shows that the proposed evaluation indexes can more accurately reflect the strength and weakness trend of the surface radiation field.The reflectivity has the greatest influence on the thermal radiation field of the building surface, followed by the emissivity, and the material type has the weakest influence. The multi-factor combination method with the strongest surface radiant thermal effect is discussed, and the internal causes are analysed.