Abstract: Yuanjiang valley is one of the most dry-hot areas in Yunnan Province. Savanna is distributed in mountains under the altitute of 800-900 meter widely.According to the Local Records of Yuanjiang County Printed in 1714, 1826 and 1922, and through our exploring to present-day vegetation,the authors give a brief view of vegetational change in Yuanjiang dry-hot mountains in the last 500 years.The paper presents that the forest cover degrees in the county were declined by increasing human population, it shows a progressive change from 75 percent in the county before the midle of 17th centry, then around 70 percent during the 18th and 19th centries, then 61.5 percent in 1958, then 27.3 percent in 1975 and finally 19.3 percent in 1982. The study shows that the main plant communities in the mountains were tropical monsoon forests even seasonal rainforest before later of the 19th centry, then the savanna was spreaded quickly.

Key words: Vegetational change