Abstract: To support the implementation of environmental quality standards for surface water revision, COD_Mn limit was researched through systematic analysis of typical watershed water quality and consulting literatures. The contents in the literatures were referred to domestic and international drinking water quality standards, the COD_Mn health hazard in drinking water and assessment on COD_Mn removal effect of different water purification technology. As an important indicator of organic pollution control, potassium permanganate index (COD_Mn) is a comprehensive index reflecting water organic pollution. Concerned on human health, COD_Mn generally to be thought not toxic. However, there is a relationship between COD_Mn and the disinfection by products concentration in chlorinated finished water. According to the survey conducted on COD_Mn concentration of typical watershed in China in 2007, COD_Mn of river, lakes/reservoir and groundwater of centralized drinking water sources was studied. The results showed that the highest COD_Mn concentration was in lake/reservoir sources with an average value of (2.70±1.40)mg/L, followed by river sources with an average value of (2.49±1.26)mg/L. The two types of water source presented seasonal variations that COD_Mn concentrations were lower from January to April and from November to December, but higher from May to October and reached the maximum value in August. COD_Mn concentration in groundwater sources was lower, compared with the other two types of water source, the average value of which is (1.11±0.81)mg/L. There was no obvious seasonal variation of COD_Mn concentration in groundwater sources. According to the “Standards for Drinking Water Quality” (GB 5749-2006) and the current routine of water purification process in China, the proposed COD_Mn concentration standard limit in drinking water sources is 4.0mg/L. The evaluation results showed that the water quality standard rate of COD_Mn concentration was 84.9%-89.0% in river-type source, 81.0%-89.6% in lake/reservoir source and 99.6% in groundwater source, respectively. In order to improve the level to meet the requirement of COD_Mn in drinking water sources, agricultural non-point pollution sources should be strengthening controlled.