[Objective] The soil moisture movement in grassland under the background of urbanization was studied in order to provide a scientific basis and technical support for improving the construction level of sponge city. [Methods] The study area was an artificial grassland at the hydraulic and hydro-ecological testing ground, located on the Yangzijin campus of Yangzhou University, Jiangsu Province. Observed rainfall data and soil moisture data were used to analyze infiltration depths under various rainfall events. Soil moisture variation processes at the study area were simulated using the HYDRUS-1D model. [Results] During light rain (<10 mm) and moderate rain (10~25 mm) events, rainfall infiltration depths at the grassland study area were not more than 15 cm and 30 cm, respectively. During heavy rain (25~50 mm) and torrential rain (>50 mm) events, rainfall infiltration depths were always more than 30 cm, and sometimes exceeded 60 cm. Root mean square errors of simulated results against observations ranged from 0.012 cm³/cm³ to 0.034 cm³/cm³. [Conclusion] Rainfall infiltration depths at the grassland area are clearly different under rainfall events with different magnitudes, and infiltration depth can generally increase with increasing rainfall amount. Additionally, the HYDRUS-1D model can accurately simulate rainfall infiltration depths under differing rainfall amounts for urban grassland areas.