Based on the monitoring on runoff water quality under different underlying surfaces of typical residential areas in Tianjin, typical rainfall was chosen to investigate the characteristics of runoff pollutants and event mean concentration(EMC). The results show that the pollution mass concentration in runoff of main roads and markets decreases with the rainfall duration and the scouring effect is obvious. The pollution concentration in runoff of roofs changes slightly with the rainfall duration and the scouring effect is weak. There are significant differences between the pollution concentrations in runoff of three kinds of underlying surfaces. The SS concentration in runoff of main roads is similar to that of markets, but much higher than that of roofs. The COD and TP concentrations in runoff ranking from high to low are markets, main roads, and roofs, and the TN concentration in runoff ranking from high to low is markets, roofs, and main roads. Suppose EMC is defined as the mid-value, the mean pollutant concentration in runoff of markets is higher than that of main roads and roofs, and the TP concentration in runoff of markets is 3 times that of main roads and 24 times that of roofs. So the runoff pollution in typical residential areas of Tianjin City is quite serious. The water quality in rivers and water environment of the City will be strongly influenced if the runoff is directly drained into rivers without any interception or treatment.