Abstract: An analytical method for the determination of trace arsenic in lead smelting wastewater by spectrophotometric with disulfoantipymethane. In 1.8 mol·L^-1 H₂SO₄ medium, arsenic reacts with disulfoantipylmethanesensitively with an absorption maximum at 331 nm. The effects of reaction conditions, such as the amount of color reagent, reaction time, reaction medium, acidity and different valence arsenicon the absorbency were investigated. The results showed that linear relationship was found in the range of 0.04-0.6 mg·L^-1 As³⁺ in 10 mL solution using a 4 cm cuvette with the reagent blank as a reference, the linear regression equation was y=1.063 x+0.001, and the correlation coefficient was 0.999 3, the molar absorptivity was 2.7×10⁴L·mol^-1·cm^-1. Test for recovery was made by standard addition method, giving values of recovery in the range of 97.0%-105%, and values of RSDs (n=5) ranged from 1.3% to 2.6%. The proposed method was applied to the determination of trace arsenic in smelting wastewater with satisfactory result.