Green roofing is a passive building technology. By using additional green roof layers, it improves the thermal performance inside the building, it also increases the green area of the city of the building roof layer outside the building. These dual effects can reduce energy consumption inside the building, and relieve urban heat island effect outside the building. In the middle and lower reaches of Yangtze River, weather in winter and summer go to extremes and is always humid and rainy all year round. The impact of extensive green roof on the building environment was verified by experimental monitoring and energy simulation. To prove the green roof effect on energy consumption of building, the temperature of a model office building in Nanjing City was monitored, temperature distribution in green roof and general roof in real-time were recorded,the result shows that the average temperature is 16 ℃ lower on the green roof . Energyplus simulation software was used to simulate the energy in the same building, the energy consume was reduced 2.6 kWh/m 2 totally when the roof have a insulation layer, and it can inhanced to 14.1 kWh/m 2 when the roof have no insulation layer. Airpak simulation software was used to simulate the effect on the environment in a residential area in Shanghai after the application of green roofs, the result shows the temperature was 0.2 ℃ than before.