Abstract: In order to explore the evolution of hydrological cycle in the agro-pastoral ecotone under changing environment, this paper takes Mu Us Sandy Land as the study area, and data of geological, hydrological, meteorological, and applies artificial water withdrawal to establish a surface（Water and Energy transfer Processes in Large river basin, WEP-L）-groundwater（Visual Modular Finite Difference Groundwater Flow, Visual-MODFLOW） joint model, the model parameters are calibrated and verified by using the monthly surface runoff data of Baijiachuan hydrological station and groundwater table data. The results show that the NSE of the monthly runoff simulation of the WEP-L model calibration and verification period is above 0.40, the R2 is above 0.65, and the relative error is within ±15%, the model is relatively accurate in simulating the monthly surface runoff process in the dry season at Baijiachuan Hydrological Station. Meanwhile, the R2 of groundwater table simulated and measured during the simulation period of four representative wells in the study area simulated by the Visual MODFLOW model is basically above 0.58, the MAE is less than 0.3m and the RMSE is between 0.028～0.265m, suggesting that the established surface water-groundwater model can be used for distributed simulation of hydrological cycle process in the Mu Us Sandy Land. On this basis, the spatial distribution characteristics of surface water-groundwater in Mu Us Sandy Land are further explored. The results show that the surface runoff and groundwater table in different regions of the Mu Us Sandy Land are significantly different, and the groundwater table is low in places with large surface runoff. From 2019 to 2020, the runoff in the Mu Us Sandy Land decreased, but the spatial distribution was basically the same, showing a gradual increase from the west to the east, and the runoff in the southeast corner of the area was the largest. The groundwater table in the area remained almost unchanged from 2019 to 2020, showing that the amount of groundwater recharge and extraction are basically the same. In terms of space, the difference in groundwater table in the adjacent areas of the southeast and northeast corners of the sandy land is relatively large, and the water table drops faster, which is similar to the topographical change. The research results can provide scientific support for agricultural water allocation in the agro-pastoral ecotone, and for the regional water resources planning and management.