To　comprehend　the　water　purification　process　of　Water　Source　Heat　Pump　(WSHP)　water　treatment　system　and　improve　the　efficiency　of　WSHP,　the　fluorescence　of　DOM　in　water　treatment　system　was　studied　with　three-dimensional　fluorescence　spectroscopy.　The　results　showed　that　the　WSHP　water　treatment　system　has　poor　effect　on　the　treatment　of　DOM,　which　has　long　been　neglected,　which　affecting　energy　efficiency　of　WSHP.　The　filter　cleaning　cycle　has　a　significant　effect　on　the　removal　of　protein　organic　components,　microbial　metabolites　and　humus.　The　HIX　index　of　water　in　the　system　smaller　than　4,　and　the　main　source　of　DOM　is　microbial　metabolites.　A　long　cleaning　cycle　will　cause　the　system　internal　sludge　clogging,　triggering　the　DOM　leak.　The　rich　fulvic　acid　and　protein　organic　components　may　be　derived　from　Cyclotella　sp.,　and　humus　may　be　derived　from　other　algae.　DOM　removal　effect　is　mainly　affected　by　the　filter　operating　cycle.　To　prevent　the　scaling　problem　in　WSHP,　more　water　treatment　measures,　such　as　frequent　cleaning　and　intensive　processing,　should　be　taken　to　enhance　the　efficacy　of　WSHP.　©　2018,　Peking　University　Press.　All　right　reserved.