Abstract:The rainfall runoff with 50% pollutant load was defined as initial rainwater, and the time (T50) accumulating 50% pollutant loading and corresponding runoff depth (D50) was selected to analyze the cumulative characteristics of pollutants during 17 rainfall events in typical domestic mountainous city, plain city, river city, etc. Taken mountainous and plain cities as examples, the cumulative characteristics of different types of pollutants in the runoff were discussed and the effects of rainfall intensity and its regional environment were studied. The results indicated that the accumulation of runoff pollutants had the same trend but exhibited different characteristics. It tended to accumulate at mid-stage in plain city while at initial stage in other cities. With rainfall intensity increased, the D50 of pollutants increased greatly while T50 declined sharply. Pollutants in mountainous city had a higher D50 and a lower T50 than that in plain city. It was suggested that mountainous cities and plain city intercepting 7.4mm and 5.2mm runoff respectively could control 50% pollutant load.