Abstract: Abstract: Background:Precipitation is the primary source of soil water in loess hilly areas, playing a crucial role in soil water recharge and the growth and development of vegetation. This study simulates and verifies the infiltration characteristics of soil moisture in retired grassland under varying rainfall conditions using the Hydrus model, providing a theoretical basis for optimizing rainwater resource utilization and enhancing the ecological environment. Methods:Seven precipitation treatments were established using a rain shelter device to simulate various rainfall variations in the field: a 60% increase, a 40% increase, a 20% increase, natural rainfall, a 20% decrease, a 40% decrease, and a 60% decrease in rainfall. Time-domain reflectometry (TDR) was employed for in situ monitoring of soil moisture content, while the Hydrus model was used to validate the infiltration processes of soil moisture under natural rainfall conditions. Results:(1) The average increase in soil water content in the top 10-20 cm for the rainfall increase treatments (31.39%) was lower than that of natural precipitation (50.17%). Conversely, the average increase in soil water content for the rainfall decrease treatments (83.11%) was significantly greater than that of natural precipitation. Soil moisture content in the 20-80 cm layer exhibited an initial increase followed by a decrease, with a slowdown observed beyond 100 cm. (2) The correlation between soil water content and precipitation was strongest at 20 cm across different precipitation treatments, with significant positive correlations observed in the 0-100 cm soil layer for both rainfall increase and decrease treatments (P < 0.05). However, correlations were weaker in the 110-140 cm and 150-180 cm layers (P > 0.05). (3) Both simulated and measured soil water contents under varying rainfall conditions followed a similar temporal trend, initially increasing rapidly and then gradually decreasing after rainfall. The root mean square error (RMSE), Nash efficiency coefficient (NSE), and correlation coefficient (R) indicated a high degree of accuracy in the overall simulation results. Conclusion:The Hydrus model effectively simulates changes in soil water content under different precipitation conditions in the grasslands of the loess hilly region. Treatments involving a 40% increase, a 60% increase, and a 20% decrease in rainfall significantly affected soil water content in this region.