Abstract: A new triazene reagent 1-(4-antipyrine)-3-(3-nitroaniline)-triazene (ANTA) was synthesized, and used as a new chromogenic reagent for cadmium(Ⅱ). In a Na2B4O7-NaOH buffer solution of pH 10.2, and in the presence of Tween-80, a stable coordination complex with the molar ratio ［ANTA∶Cd(Ⅱ)］ of 2 to 1 was formed, with its absorption maximum at the wavelength of 508 nm. Value of apparent molar absorptivity was found to be 3.4×105L·mol-1·cm-1. Beer′s law was held in the range of 30.0-450 μg·L-1, with detection limit (3σ/k) of 10.0 μg ·L-1. The proposed method was applied to the determination of cadmium in waste water samples, giving results in consistency with those obtained by AAS. Average values of recovery found were 103.5% and 4% respectively.