Experiments were conducted to investigate the degradation of 2,6-dinitro- -cresol (DNPC) in the chlorine dioxide (ClO ) catalytic oxidation process. Pure aluminum oxide was used as the catalyst in this process. The degradation of DNPC by ClO using aluminum oxide as catalyst was systematically studied by varying the experimental parameters, such as pH values, catalyst dosage, the initial concentration of DNPC and ClO , reaction time, etc. Under optimal condition (DNPC concentration 39 mg·L , ClO concentration 0.234 g·L , reaction time 15 min, catalyst dosage 4.7 g·L and pH 4.32), almost complete degradation of DNPC can be achieved. The kinetic studies revealed that the ClO catalytic oxidation degradation of DNPC followed pseudo-first-order kinetics with respect to both ClO and DNPC concentration. The repetitive use of the catalyst was investigated along sequential feed-batch trials. The catalyst performed efficiently after five runs. In addition, a simple and convenient method for the determination of ClO in water was developed by using acid chrome black 7 (MB 7) spectrophotometry in this paper.