The　control　function　of　potassium　permanganate　and　chloramines　to　trihalomethane　(THMs)　formation　in　the　combined　pretreatment　process　was　approached.　The　results　showed　that　THMs　formation　can　be　effectively　controlled　by　the　synergistic　pretreatment　of　potassium　permanganate　and　chloramines　within　the　normal　range　of　potassium　permanganate　dosage　in　the　drinking　water　treatment　process　(below　2　mg/L).　The　control　effect　of　potassium　permanganate　to　THMs　formation　is　the　results　of　combined　action　with　multiple　affecting　mechanisms.　The　combined　pretreatment　process　of　potassium　permanganate　and　chloramines　may　further　reduce　THMs　formation　on　the　premise　of　improved　inactivation　effects,　compared　with　individual　chloramine　pretreatment　of　the　same　total　dosage.　Therefore,　the　treated　water　quality　in　both　the　aspects　of　chemical　safety　and　microbial　safety　can　be　improved　after　the　pretreatment　of　polluted　raw　water　by　this　combined　technique.