Abstract: In order to reduce the initial runoff pollution in the rural residential area, a composite engineering consisting of a settling tank, an adjusting tank and a water-collecting flowerbed were constructed near Yuncun Village, Qianhuang Township, Changzhou City to collect the initial runoff and drainage from the catchment area (about 6.00 hm²). Based on the composite engineering, the monitoring test was done. Water samples were taken at the water inlet, the water outlet of the settling tank, the adjusting tank and water-collecting flowerbed. The physical and chemical indexes of water samples, including temperature, pH, dissolved oxygen (DO), total nitrogen (TN), ammonia nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), total phosphorous (TP), chemical oxygen demand (COD_Cr) and suspended solids (SS), were monitored to analyze the total removal rates of pollutants and estimate the reduction of pollutants in the initial runoff by the engineering. The results show that the average values of the total removal rates of TN、NH₄⁺-N、NO₃^--N、TP、COD_Cr and SS were 39.1%, 47.4 %, 29.0%, 33.3%, 33.4% and 43.1%, respectively. The scouring effect to the composite engineering caused by the storm runoff of July 15, 2020 was significant when the pollutant concentrations in the effluent of the engineering were higher than those in the influent except for NH₄⁺-N and COD_Cr. The correlation between the total removal rates of TN and NH₄⁺-N was extremely significant (P < 0.01), and the correlation between the total removal rates of COD_Cr and SS was extremely significant (P < 0.01). The composition of TP in the influent was mainly dissolved phosphorus. Due to submerged volume in the engineering, the plant biomass was increased and the denitrification capacity of the system was improved, which in turn promoted the reduction of nitrogen and phosphorus pollutants. Base on estimation of annual rainfall, the annual reduction amount of TN, TP and COD_Cr in runoff or drainage by the composite engineering were approximately 2.49, 0.29 and 20.94 kg·a^-1, respectively, and the effluent from the engineering can be used for reclaimed water reuse. How to miniaturize and standardize the composite engineering and improve its purifying efficiency and shock resistance should be the priorities in the future researches, so that it can be promoted and applied in more rural residential areas in Taihu Lake Basin.