By taking a built square in Guangdong as the objective,the temperature,humidity and illuminance of the exterior of the modular ecological wall are quantitatively compared with those based on the bare wall,so as to reveal the effects of the modular ecological wall on the exterior light-thermal environment of the building.The re- sults show that (1) as compared with the bare wall,the modular ecological wall can significantly increase the hu- midity and decrease the temperature，and it causes a lower illuminance; (2) in comparison with the bare wall,the modular ecological wall reduces the exterior temperature by up to 5. 1℃ in a day,and it can significantly re- duce the energy consumption of the building; (3) the relative humidity of the exterior of the modular ecological wall is at most 23% higher than that based on the bare wall; and (4) the modular ecological wall has a better shading effect than the bare wall; specifically,the former can reduce the illuminance by 99. 4% at most.There- fore,the modular ecological wall is an effective,active way of thermal insulation and energy saving,which can produce good comprehensive benefits in energy saving.