Abstract: In a H2SO4 medium,a red complex was formed by the reaction of Cr(Ⅵ) with alizarin blue S for 20 min at room temperature,having the absorption maximum at the wavelength of 520 nm.Beer′s law was kept in the range of 0.001-0.5 mg· L-1.Detection limit (3s/k) of the method was 0.87 μg·L-1,and value of apparent molar absorptivity (ε) found was 4.86×105L·mol-1·cm-1.The proposed method was used in the determination of Cr(Ⅵ) in plating waste solution and plating discharge solution,the values of recovery were in the range of 95.0%-105.0%,and values of RSD′s (n=5) were less than 5.1%.