Combining field monitoring and laboratory analysis, this paper analyzes COD_cr and TSS fluxes of a typical suburb discharge sewage in Dianchi Lake catchments. We use the pollution load of urban rainfall runoff to estimate the pollution load of suburb rainfall runoff and analyze the ratios of COD_cr and TSS caused by rainfall runoff to the total load. Results show that by suburb discharge sewage per capita load, COD_cr is 9. 58～10. 57 kg/ a and TSS is 2. 88～3. 14 kg/ a and by the suburb pollution load of rainfall runoff, COD_cr is 1. 166～1. 458 t/ (hm² ·a) and TSS is 0. 729～1. 808 t/ (hm² ·a) in the Dianchi Lake catchments. Throughout the year, COD_cr and TSS caused by rainfall runoff account for 10. 96 %～15. 35 % and 25. 73 %～35. 89 % of the total catchment area of emission pollution load, respectively. Control of rainfall runoff pollution is one of the ways to mitigate non-point source pollution of suburb in the Dianchi Lake catchments.