Multi-objective optimization of a purified terephthalic acid (PTA) oxidation unit is carried out in this paper by using a process model that has been proved to describe industrial process quite well. The model is a semi-empirical structured into two series ideal CSTR models. The optimal objectives include maximizing the yield or inlet rate and minimizing the concentration of 4-carboxy-benzaldhyde, which is the main undesirable intermediate product in the reaction process. The multi-objective optimization algorithm is based on Neighborhood and Archived GA, proposed by the authors. The performance of NAGA is further illustrated by application to the title process.