[Objective] To analyze the decontamination condition of urban rainwater in soil and the effect of rainwater runoff pollutants on soil environmental. [Methods] Based on full understand of soil properties and the quality of runoff in Xi'an City of Shaanxi Province, the urban soil system and rainwater runoff device were simulated to analyze the reducting functions of topsoil on rainwater runoff pollutants in the process of infiltration, and the change of the basic physical and chemical properties of soil. [Results] As the soil layer thickness was 20 cm, total rainwater penetration was 6 000 ml, and the runoff time was 3 h, the removal rate achieved above 40% both in bare soil and green fields systems on simulated rainwater pollutants. The soil density and pH value did not changed. But for the content of nitrogen, effective phosphorus, and soil organic matter, from in the original soil to green fields and bare soil, they changed from 54.95 mg/kg to 65.10 mg/kg and 68.60 mg/kg, 59.23 mg/kg to 82.39 mg/kg and 39.93 mg/kg, 18.32 mg/kg to 19.28 mg/kg and 14.04 mg/kg, respectively. [Conclusion] The effect of green fields on runoff water treatment is significant. In the process of infiltration, soil present significant effect on removal of ammonia nitrogen, and soil basic physical properties show little change within a short time.