[Objective] This paper aims at exploring the relationship between the spongification degree and the quality of surface runoff, so as to provide guidance for the construction of sponge facilities alleviating current surface runoff pollution.[Methods] Jiaxing City is one of the pilot sponge cities in China and was taken as a study area, where 20 projects with different spongification degrees were selected as analysis units. Indicators were established reflecting the spongification degree, such as the type, quantity and layout of sponge facilities. Redundancy analysis, partial least squares method and Origin fitting equation were introduced in the study.[Results] ① Neither the water quality of residential area nor of public buildings areas attained class Ⅳ of surface water and secondary standards for sewage discharge. The water quality of the sponging-transformed area was generally better than that of the untransformed area. ② The area ratio of green space to effective impervious area(EIA) is the key factor affecting runoff water quality, of which suspended solids(SS), bichemical oxygen demand(BOD₅) and chemical oxygen demand(COD) are the mainly affected indicators. ③ In order to make the runoff water quality meet the requirements of sponge city construction, thresholds for the control of land use under different spongification degree should be different.[Conclusion] When EIA≈0, the proportion of green space should be no less than 31%; when EIA=0.04(TIA)^1.7 (TIA is the total impervious area), the proportion of green space should be no less than 38.5%; when EIA=TIA, the proportion of green space should be no less than 47%. The ratio of EIA should not exceed 9% under the current urban green space ratio standard(about 35%).