The aim of this research is to observe the decrease in lignin content and wastewater quality from oxygen delignification process of kraft-pulped Eucalyptus pellita. In pulp production, conventional kraft cooking is carried out with five active alkali charge (16%, 17%, 18%, 19%, and 20%), with 25% sulfidity in addition to H factor of 800. Oxygen delignification occurs in medium consistency (10%) and 2 bar oxygen pressure, in addition to delignification with an alkaline charge of 20 g/L and a temperature of 85°C. In the kraft pulping process, the increase of alkali active causes a decrease in lignin levels. In the next process, oxygen delignification shows that longer reaction time causes a decrease in the levels of lignin, COD, and BOD5. The information from this study will be helpful to the future implementation of kraft pulping integrated with oxygen delignification process in actual pulp mill applications of Eucalytus pellita.