Abstract: The Bashang Plateau of Chengde City is located in an ecologically fragile area in the north of China. In recent years, it is facing the problems of natural lake shrinking and local groundwater level declining. In order to find out the reason of the shrinkage of Moon Lake in the eastern part of the Bashang Plateau, and to better serve the ecological environment supporting capacity construction, the authors had systematically analyzed the ecological environment changes in the region and the reasons for the shrinkage of Moon Lake based on field investigation and detailed data analysis. We found that:(1) The water surface area of Moon Lake was a period of rapid growth from 1975 to 1993, and the largest area in 1993 at 0.43 km², it was a slow shrinkage period from 1993 to 2013 and a faster shrinkage period after 2013.(2) On the interannual scale, rainfall and evaporation are all increasing in the Moon Lake area, however, the increase in evaporation caused by temperature rise and changes in underlying surface conditions is more obvious. (3)The impact of human activities on the lake area cannot be ignored, and the area of artificial forests has increased, the road hardening after tourist, groundwater extraction and increased drinking water for horses after tourism development that may be the important reasons for the rapid shrinkage of the lake. (4) It is recommended that the Bashang Plateau area develops water-saving eco-tourism in the future, and at the same time, implements some restrictions on groundwater extraction to strengthen water conservation and protection. in the lake and surrounding areas.