Colors have a complex molecular structure, often toxic, mutagenic, nondegradable biologically, and stable, which, when they enter the environment, cause environmental problems. Advanced oxidation processes are the most efficient and effective methods for decomposing dangerous organic contaminants which are resistant and nonbiodegradable in aquatic environments. The study aimed to determine the efficiency of the ozonation process with calcium peroxide for the removal of reactive blue 19 dye from textile wastewater. Synthetic samples were prepared with blue dye concentrations of 10-300 mg/L. The removal efficiency of reactive blue 19 dye and chemical oxygen demand (COD) by ozonation with calcium peroxide in different conditions of pH, calcium peroxide concentrations, contact time, concentration of the reactive blue 19 dye, and 1 g of ozone/min was examined. The optimal conditions for synthetic samples were obtained. The maximum removal of blue dye and COD with a concentration of 5 mg/L reactive blue 19 dye, pH = 3, 0.025 mg/L of calcium peroxide, contact time of 40 min, were 100% and 85.6%, respectively, in synthetic samples and 90% and 76.5%, respectively, in real samples.