As a reserve area of water resources in Beijing, the dynamic change of groundwater level in Xishan region is of great significance to water resources management. Time series analysis is an effective tool to predict the dynamic change of groundwater level.In order to investigate the variation trend of groundwater level in Xishan region, the paper built the dynamic variation model of groundwater level by use of long monitoring data series of groundwater level in Xishan region of Beijing through fitting the trend component, periodic component and stochastic component of the series.The accuracy test of model indicated that fitting degree of model is good and the groundwater level in this region will appear the state of dynamic balance in the following five years.