［Objective］ Soil moisture spatiotemporal dynamics in fixed sand-dunes （planted with Hedysarum scoparium） in eastern Yellow River sandy land in Ningxia Hui Autonomous Region were investigated， to provide scientific insights for sustainable desertification control and effective evaluation of sand stabilization measures. ［Methods］ The HYDRUS-1D model was employed to simulate the vertical distribution （0—150 cm profile） and temporal variations in soil moisture in fixed dunes. The model performance in eastern sandy land of Yellow River in Ningxia was evaluated using the coefficient of determination （R²）， root mean square error （RMSE）， and relative error （RE）. ［Results］ ① Rainfall infiltration exhibited threshold-dependent characteristics： infiltration depth was limited to <5 cm when precipitation <2.2 mm， 5—15 cm for 3.6—8.2 mm rainfall， and 15—30 cm for 10.8—22.8 mm rainfall. ② The model demonstrated satisfactory performance in simulating soil-water content across most depths （calibration R²=0.756， validation R²=0.773； RMSE=0.071% and 0.064%； RE=0.030% and 0.032%）. Although surface （5 cm） and deep layer （125 cm） simulations showed lower accuracy， intermediate layers （15， 30， 50， and 80 cm） achieved better results （R²=0.571—0.849， RMSE=0.0001%—0.042%）. ［Conclusion］ The infiltration patterns varied significantly across rainfall events， showing a positive correlation between the amount of precipitation and infiltration depth. The HYDRUS-1D model proved suitable for simulating the soil moisture dynamics in this arid sandy ecosystem， with simulations closely matching field observations.