A method for simultaneous determining of chromium (III), aluminum (III) and iron (III) by catalytic kinetic spectrophotometry was realized based on the principle that Cr (III) Al (III) and Fe (III) catalyzing simultaneously the reaction of brilliant cresyl blue with hydrogen peroxide in a CH₃COONa-CH₃COOH medium. It was found that the catalytic effects of the three metal ions were not synergistic. The recoveries of the method ranged from 97.9% to 101.9% with the RSDs of 2.7% to 4.2% and relative errors of -4.3% to 4.7%.