The effect of water quality characteristics on oxidative decomposition of yarn dyeing wastewater by ozonation combined with hydrogen peroxide was investigated. As a sample, it used the wastewater(Sample a) of rinsing and the treatment water(Sample b) which was treated with the coagulation-precipitation and the activated sludge process of mixed wastewater of scouring, bleaching and dyeing. At ozone single processing, the decolorization of both samples proceeded with increasing amounts of ozone injected. Contrarily, the BOD values of theirs were increased, respectively. In the case of the treatment with combination of ozone and addition of hydrogen peroxide, the decolorization of sample a and b were advanced in comparison with the case of ozone single processing. The BOD values of theirs showed the decrease tendency. However, by the change of the supply balance of the amount of injection of ozone and the addition of hydrogen peroxide, the removal of coloring and BOD etc. of samples had not increased so much. Therefore, it is necessary to keep the optimum conditions of the concentration of ozone and hydrogen peroxide in wastewater.