The soil column was structured to simulate the sunken lawn and three processes were simulated, including rainfall and runoff process, surface erosion and vertical infiltration process, pollutant migration and transformation process. Results show that sunken lawn is a sink and has significant effects for stormwater pollution. The overall reduction rates of CODCr, TN and ammonia is 71.01±1.75%, 69.00±1.78%, and 64.39±1.84% respectively. The reduction effect is related to the pollution load, hydraulic loading and antecedent dry period.