Under the condition of pH=2.7,there was a significant inhibition of BrO₃^2- on the chromogenic reaction of Fe(Ⅱ)-BPY system,so a new method was established for determination of trace BrO₃^2- in drinking water.The influence of pH,ultrasonic time,dosage of chromogenic agent and coloration time on the determination of trace BrO₃^2- was discussed.Under the comfirmed conditions,the absorbance value was linearly correlated to bromate concentration in the range of 0.2~1.0 mg/L with the correlation coefficient of 0.999 3.The detection limit was found to be 0.002 6 mg/L.This method was applied to determine the content of BrO₃^2- in drinking water and RSD was less than 5%（n=3）,the recoveries were in the range of 92.8%~101.5%,which can satisfy the requirements for determinating trace BrO₃^2- in drinking water.