Abstract: The permanganate index in surface water and groundwater was determined by ultraviolet-visible spectrophotometry. The detection limit of the method was 0.05 mg/L and the recoveries were 95.0%~100.5% with precision of 1.01%~1.20%RSD (n=5). The analytical results from this method are consistent with those determined by standard volumetric method. The method provides the advantages of high sensitivity and precision, high efficiency, less cost and is suitable for the determination of permanganate index in clean or slight polluted surface water and groundwater samples with chloride content of <300 mg/L.