In　this　paper,　the　pre-magnetization　of　sludge　was　carried　out　using　electromagnetic　field,　and　the　effect　of　electromagnetic　field　intensity　and　time　on　the　coagulation　efficiency　was　investigated.　The　results　indicated　that　the　turbidity　and　DOC　removal　efficiency　of　recycling　magnetized　sludge　can　be　improved,　the　removal　of　which　was　3.7%　and　32.4%　respectively　higher　than　the　cases　without　electromagnetic　field.　Sufficiently　large　magnetic　field　intensity　and　magnetization　time　played　a　significant　effect　on　the　enhancement　of　the　coagulation　efficiency.　The　Zeta　potential　of　the　mixed　water　and　sludge　increased　by　electromagnetic　field　and　the　flocs　characteristics　were　obviously　improved,　accordingly　the　flocs　had　bigger　growth　rate,　average　flocculation　index　and　average　flocs　size　with　denser　and　regular　structure.　©　2016,　Chinese　Society　for　Environmental　Sciences.　All　right　reserved.