[Objective] The lagging infiltration recharge in south margin of Mu Us sandy land and parameter sensitivity of numerical model were studied in order to provide scientific basis for rational exploitation and utilization of groundwater resources and protection of ecological environment in this area.[Methods] Lagging infiltration recharge was analyzed based on field monitoring data, and sensitivity analysis of numerical model parameters was conducted using ratio of variation(ROV).[Results] The response depth of water content to the precipitation was 3~10 cm in small rain scenario, and 30~60 cm, 60~90 cm, more than 90 cm in middle, heavy and storm rain scenarios. The groundwater recharge was approximately 4~11 h lagged. Sensitivity analysis showed that saturated water content (θ_s) was the most sensitive parameter to the bottom flux.[Conclusion] The response depth of water content are linearly correlated with the precipitation and the groundwater recharge lag time has a positive correlation with θ_s.