Abstract: For purpose of exploring the laws of how the relative humidity changes in the sunlight green house located in high altitude and low temperature areas and thus achieving the prevention from and reduction of natural disasters and sustainable development for agriculture, with the utilization of the micro-climate observation data for sunlight green house and materials from the weather station in the national modern agricultural demonstrative zones in the eastern agricultural areas of Qinghai Province and by means of mathematical statistics method, the laws of change regarding to the various sky conditions and different seasons in high altitude and low temperature areas were analyzed. The results indicate that: Firstly, the daily change and yearly change of average relative humidity in the green house of high altitude and low temperature areas during the test turned out to be the same, the tendencies of both of which represented as the “single trough” line. And between 0:00 and 8:00, the relative humidity in the green house stayed in a stable high humidity condition. Secondly, the daily change amplitude was observed to be at its maximum in sunny days as the relative humidity rose and fell rapidly; in rainy days, the relative humidity rose and fell in slowed down speed, with the daily change amplitude decreased accordingly. Thirdly, the relative humidity correlation inside and outside of the green house in rainy days was larger than that in cloudy days and sunny days; 8:00-11:00 in sunny days, 16:00-22:00 in cloudy days , and 16:00-19:00 in rainy days the correlation was poor. Fourthly, both of the minimal and maximal values concerning the average relative humidity within one year appeared in the sunny days of winter, and between 16:00 and 19:00 in all of the four seasons the relative humidity rose fastest.