Abstract: The formation of Arsenic-Bismuth-Molybdenum Blue and optical characteristics of its reducing products were studied. It was found that the colour producing products have an absorption band at 825nm, an apparent molar absorptivity of 1.54×104, an over 8 hour stability at room temperature, a hnearity range of 0～40 μg As per 10 mL and a correlation coefficient of 0. 9995. The use of QIU’ s Arsenic Analyzer allows Arsenic in water to be separated as AsH3 giving off from water.