【Abstract】 The indigo carmine was reduced by using cheap,easily attainable and non poisonous reagents. Therefore, a special reagent was developed to measure the concentration of dissolved oxygen in water in situ . The molar absorption coefficient of the method is 1 35×10 4, and its dynamic linear range is 0-27 mg/L linearity coefficient of 0 997. The most oxidizing species, such as Cl 2, ClO -, Cu 2+ , Fe 3+ , V 5+ , and As(Ⅴ), do not interfere the determination. It takes no more than 1 min to analyze one sample. The method was applied to determining some practical samples and all the results obtained were satisfactory.更多还原