Abstract: The Chromogenic reation of Cr(Ⅲ) with arsenazo Ⅲ have been studied. The results show that complex formation reation can be complete by heating at 100℃ for 5 min. The most absorption band of the complex lies at 610 nm. The apparent molar absorptivity is 2.1× 10⁴L mol. cm. Lambert-Beer law is obeyed for Cr(Ⅲ) in the concentration range 0~60 mg/50 mL. The range of the recovery is 95%~100%. The metbod has been applied to the determination of Cr(Ⅲ) in water and industriat water water.