Abstract: Microbial inactivation efficacy of many pre-oxidants can be influenced by pH value of polluted water. Microbial inactivation effects are compared with individual application process of chlorine, chloramines or potassium permanganate, and with combined application process of potassium permanganate with chlorine or chloramines, to investigate more effective pre-oxidants. The results show that the inactivation effects of several pre-oxidants are interfered to different degrees by pH value. The advantage of combined application process of potassium permanganate with chlorine or chloramines become more obvious with increasing of pH value, compared with individual application process of chlorine and chloramines under same total dosage. The inactivation effects are increased 0.14 and 0.25 logarithmic grades with pH = 7, respectively; and 0.95 and 0.55 logarithmic grades with pH = 9, respectively. Because pH value of natural water is normally within range of neutral or weak alkaline, a newly safe pre-oxidation technique of the combined application process of potassium permanganate with chlorine or chloramines of the is presented for polluted water treatment.