With the rapid urbanization and continued improve to control urban point source pollution in China, the ratio of urban surface runoff accounted for pollution load of receiving water will be raised increasingly and pose a serious threat to urban water body. "Green" roofs, also referred to as vegetated or ecology roofs, are of the important technologies for controlling urban nonpoint source pollution, which has been taken as an important component of technical system in many advanced concepts for the management of urban stormwater runoff. Green roof has several beneficial effects in an urban setting, such as their ability to retain and detain roof stormwater runoff, reduce urban heat islands, improve air quality, provide wildlife habitats, and their esthetic value. However, there is a very important aspect that has often been overlooked in previous studies is the quality of the runoff water from green roofs. Therefore, it is very important to investigate runoff water quality from green roofs for its popularization and application. In the paper, we investigated water quality of storm runoff from green roof, asphalt roof (control roof), dry-wet deposition and rainfall from May to December, 2011, and calculated the pollution load of them, and analyzed the effect of rainfall characteristics on runoff water quality using multivariate statistical analysis. Compared the water quality from green roof, asphalt roof (control roof), dry-wet deposition and rainfall, we found that the green roof was a sink of total suspended solids (TSS), because the average TSS concentration of the green roof (20.42 mg/L) was significantly lower than on the asphalt roof (67.04 mg/L) and was also lower than that of the dry-wet deposition (36.53 mg/L) samples. The green roof can neutralize the pH from 5.61 to 6.84. The green roof is non-source and non-sink for total phosphorus (TP), dissolved copper (DCu) and dissolved zinc (DZn); conversely, the green roof was a source of electrical conductivity (EC), total nitrogen (TN), ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), chemical oxygen demand (COD), biochemical oxygen demand after 5 days (BOD₅) and dissolved lead (DPb), because the average concentration of there parameters of green roof was significantly higher than of the asphalt roof, dry-wet deposition and rainfall. However, considered about the pollution load from green roof, asphalt roof (control roof) and dry-wet deposition, we noticed that the green roof was a sink of NH₄⁺-N, TSS and BOD₅, the green roof is non-source and non-sink for TN, DPb, DCu, DZn, TP and COD, conversely, the green roof was a source of NO₃^--N. Compared the pollution load between green roof and asphalt roof (control roof), 90.53% of TSS, 49.38% of TP, 41.31% of BOD₅, 36.48% of COD, 35.45% of NH₄⁺-N, 28.27% of DZn and 14.20% of DPb could be abated, however, 821.02% of NO₃^--N and 275.48% TN could be added; The concentration of the pollutants of green roof runoff were negatively correlated with precipitation, rainfall duration and rainfall intensity, however, there was positive correlation with the antecedent dry weather period. The results can provide a basis for design of the green roof and scientific assessment the effect of the green roof to runoff water quality.