In order to know the characteristics of rainwater runoff pollution in mountain city, a typical mountain area with large slope and high green space ratio was selected to study the spatial and temporal distribution characteristics of pollutants in initial rainwater under different rainfall levels and different underlying surfaces,and to study the correlation between different pollutant indexes. The results showed that runoff pollution had the maximum value at the beginning of rainfall, then the pollution indexes decreased rapidly with time, and this phenomenon was strengthened by the heavier rain. The pollution order of rainwater runoff on different underlying surfaces from slight to serious was brick>hardened pavement>green space, and the pollution order of runoff water quality in the early stage of different rainfall intensities was moderate rain> heavy rain>rainstorm. The total nitrogen (TN) in surface runoff in the study area was mainly dissolved, while the total phosphorus (TP) was mainly particulate. The particulate nitrogen and phosphorus in runoff of green place was significantly higher than that of other underlying surfaces, and the particulate nitrogen and phosphorus in rainwater runoff under rainstorm was also significantly higher than that of other rainfall intensities. Under different rainfall intensities and underlying surface conditions, suspended particulate (SS) matter was highly positively correlated with permanganate index (CODMn ), TP, TN, total dissolved phosphorus (TDP) and total dissolved nitrogen (TDN). It shows that there is a certain degree of soil erosion in mountainous green space, and the pollution load is more concentrated in the initial rainwater, and it is more obvious with the increase of rainfall intensity. SS has a significant impact on the concentration of pollutants. Therefore, controlling the SS content in the initial rainwater is an effective way to reduce the pollutant content of rainwater runoff in mountainous cities.