Moringa oleifera Lam. is a plant with high nutritional value for h~mans and livestock. 'Several studies also showed that the extract of the seeds is antibacterial. The experiments were executed to evaluate the antibacterial activity of Moringa oleifera seed extracts against E.coli, Salmonella, Staphylococcus, aerobic bacteria and direct wastewater samples, wastewater samples from biogas of pig farms. The results showed that Moringa oleifera seed extract has strong inhibitory effect on growth of gram-positive Staphylococcus, reduces the number of aerobic bacteria, kills bacteria in aerobic and anaerobic of direct wastewater, and kills aerobic bacteria from the wastewater discharged from biogas.