The purpose of the study is flush characteristics of urban runoff pollutant on different underlying surface. Select 5 typical hardened surfaces in Changzhou City and monitor the change process of rainfall runoff pollutant from March to August in 2015. The results showed that event mean concentrations (EMC) of pollutants in road runoff were higher than that of roof runoff. For road runoff, SS concentration was higher than the water quality standards by 1.34 times; COD concentration was higher than the water quality standards by 2.59 times. For the roof runoff, COD concentration was higher than the water quality standards by 1.8 times; and TN concentration was higher than the water quality standards by 2.6 times. For the roof runoff, the dissolved-bound fraction was 72.78% for COD, 57.99% for TN. For road runoff, the dissolved-bound fraction was 61.59% for TN. The pollutant concentrations were commonly higher at the initial stage, while decreased with prolonging of the rainfall time and gradually became stable at the later stage. The initial concentrations of pollutants from the underlying surface were as follows: concrete ground, asphalt ground, paved ground, flat roof and slope roof. During the rain flush, the concentration of pollutants on the underlying surface increases with the increase of the intensity of the rain which was fluctuated. The intensity of the first flush intensity varied by surface and was most intense for the flat roof, followed by the slope roof, then the asphalt road and finally the concrete road. Rainfall in pre-period was intensive and pollutant concentration was exponentially attenuated. When rainfall changes smoothly, the concentration of pollutants was stable firstly and then attenuation. When the rainfall was sparse in pre-period and intensive in the late-period, the curves of pollutant change type was multi-peak type. The index flush model had good effect to pollutant runoff simulation, the flush coefficients of COD on the slope roof, flat roof, and concrete road were 0.871, 0.765, and 0.025 mm⁻¹, the roof flush intensity was much larger than the ground. The flush coefficient of dissolved-bound of COD and granular-bound of COD was similar on the slope roof. The flush coefficient of granular-bound of COD was greater than the dissolved-bound of COD on the flat roof and the concrete road.