The endek industry produces low-biodegradable wastewater, which is very difficult to be treated using biological treatment. For this reason, this study was aimed to improve the quality of wastewater for endek textile wastewater using the combination of ozone oxidation process as pretreatment and anoxic-aerobic activated sludge. The ozone reactor volume 3L and at the ozone dose of 0.05 mg/minute. The BOD/COD of endek wastewater increased to 0.38 after ozone treatment and the application of anoxic-aerobic activated sludge treatment. The anoxic-aerobic experiments were conducted in batch process and consisted of activated sludge. Conventional anoxic-aerobic treatment can reach color and COD removal of 30 and 32%, respectively, without pre-treatment. The ozone pretreatment can increase color and COD removal up to 76.6% and 86.9%, respectively. Based on the effluent standards of textile wastewater quality the COD, BOD5, and total ammonia (NH3-N) parameters have met the quality standards.