Abstract: In order to improve the cave＇s environmental quality and provide scientific basis for the protection of cave landscape, two times monitor on the spot from 1 to 5, May and 28 to 30, July, 2006 have been taken to monitoring the regime of temperature and humidity as well CO2 concentration of the Jiutian cave with the number of tourists. It is proved that the CO2 concentration is affected by the number of tourists and is of obvious accumulative effect. Among the monitoring spots, No. 11 （Lingxiaoyu Tower） has the highest average daily CO2 concentration with the value 11 250 ppm that is very rare all over the world. The temperature of the cave is affected both by cave drip water and by the shapes of the cave, and changes to some extent. Humidity of the cave is affected by the weather but also by respiration of the tourists especially in the enclosed sections of the cave.