Effluent of wastewater treatment plants as an alternative water source in many applications and restrict the uncontrolledexploitation of high-quality water resources. Before the design and implementation of wastewater treatment plants, youshould use the methods based on scientific reasonable assumptions to determine an appropriate process of treatment. Theaim of this study is to select the optimal wastewater treatment process in an industrial research complex using multi-criteriaanalysis. The present study used the Analytic Hierarchy Process (AHP) to select the optimal process of human’s wastewatertreatment plant and processes such as Septic tanks, stabilization ponds, aerated lagoons, activated sludge, tricklingfilter and MBBR were assessed technically, operationally, economically and environmentally. The results showed that theMBBR process, activated sludge, trickling filter, septic tanks, aerated lagoons and stabilization ponds with final weightsof 0.280, 0.197, 0.162, 0.133, 0.116 and 0.112 were ranked first to sixth respectively. The sensitivity analysis also showedthat the changes in weight of AHP criteria don’t show significant changes in the final result and MBBR process has beenin first place almost in all modes unless the relative weight of economic and environmental criteria are replaced. In thiscase, Septic tanks were slightly higher than MBBR. According to the results, the highest priority of treatment processesbelonged to MBBR.