An experiment is conducted on the impact of green roof on Indoor Human Thermal Comfort. The result shows that the temperatures of the building walls and indoor air fall for certain degrees, and that is good. But unfortunately, the relative humidity of the indoor air rises. Totally speaking, the whole effect is changed from feeling warm to basically acceptable. When the requirement of the indoor environment is high, it is impossible to be satisfied by exploiting green roof solely, other methods, such as using night ventilation, electric fans or air-conditioners, should be taken at the same time.