The　effects　of　energy　density,　power　polarity　and　electrode　interval　on　removal　efficiency　of　microorganisms　and　particulates　in　indoor　air　were　investigated　using　a　needle-to-hole　DC　corona　discharge　plasma　reactor.　The　removal　mechanisms　were　analyzed.　The　results　show　that　the　DC　corona　discharge　plasma　reactor　has　good　performance　in　removing　microorganisms　with　different　sizes　(0.65~2.1　μm,　>2.1　μm)　and　coarse　particulates　(TSP　and　PM10),　however,　incapable　of　removing　fine　particulates　(PM2.5).　Compared　with　positive　DC　corona　discharge,　negative　DC　corona　discharge　behaves　better　in　removing　paticulates,　however,　worse　in　removing　microorganisms.　Under　the　same　conditions,　the　removal　efficiency　of　fungi　is　higher　than　that　of　bacteria.　These　observations　can　be　explained　by　the　difference　in　the　composition　of　plasma　generated　by　positive　and　negative　DC　corona　discharge　as　well　as　different　resistance　abilities　of　different　microorganisms　to　plasma　oxidation.　As　microorganisms　can　be　inactivated　by　plasma　species　besides　being　removed　by　electrostatic　precipitation　in　the　electric　field,　its　removal　efficiengy　is　higher　than　that　of　particulates　under　the　same　conditions.