In　this　paper,　a　performance　test　of　a　hydraulic　diaphragm　metering　pump　using　R123　is　conducted.　The　interaction　relationships　of　key　parameters　of　the　pump　and　its　influence　on　the　performance　of　the　ORC　system　are　analyzed.　The　application　feasibility　of　the　pump　has　been　proved　by　comparison　to　previous　studies.　The　results　indicate　that　the　mass　flow　rate　of　the　pump　varies　from　0.23　t/h　to　2.06　t/h　and　is　mostly　independent　of　outlet　pressure.　Both　power　input　and　actual　efficiency　of　the　pump　increase　with　stroke;　the　actual　efficiency　reaches　up　to　a　maximum　of　88.27%.　The　specific　speed　decreases　with　the　increase　of　outlet　pressure.　Moreover,　the　actual　net　power　output　and　thermal　efficiency　of　the　ORC　system　increase　with　evaporating　temperature.　Actual　net　power　output　is　more　sensitive　than　thermal　efficiency　to　stroke.　The　thermal　efficiency　presents　a　nonlinearly　rapid　decline　trend　with　the　increase　of　specific　speed.　Back　work　ratio　(BWR)　can　reach　up　to　a　maximum　of　0.93.　Thus,　the　power　input　of　working　fluid　pump　is　not　negligible　in　the　ORC　system　and　the　assumptions　of　actual　efficiency　of　pump　should　be　dependent　on　experimental　results　according　to　various　operating　conditions.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.