Miniature　axial　flow　pump　(M-AFP)　is　a　ventricular　assist　device　that　supports　the　failing　ventricle　in　advanced　stage　heart　failure.　In　the　past　several　years,　we　have　developed　two　types　of　M-AFP　aiming　for　children.　In　this　paper,　mechanical　performance　of　them　are　tested　and　analyzed　in　order　to　help　us　find　out　their　differences　in　nature.　A　simulative　circulative　apparatus　is　designed　that　can　be　used　to　quantitatively　predict　the　mechanical　characteristic　parameters　of　the　pumps　and　their　relationship.　Under　the　condition　of　load　pressure　invariance,　we　mainly　test　the　change　of　blood　flow　with　these　two　pumps　respectively.　The　type　A　has　a　volume　of　47ml;　with　external　diameter　of　26mm　and　length　of　72mm.　The　simulative　cardiac　flow　attains　3-4L/min　under　the　pressure　of　100mmHg,　which　is　enough　to　assist　the　left　ventricular　of　children.　In　all　the　two　pumps,　rotate　speed　of　impeller　and　flow　rate　of　blood　present　positive　mutuality　with　pressure　invariance.　Besides,　comparing　with　type　A,　the　type　B　has　smaller　volume,　and　it　is　much　easier　for　type　B　to　increase　rotate　speed　of　the　pump　and　comparably　reduce　energy　consumption.　Apart　from　the　characters　of　smaller　volume　and　simpler　configuration,　the　output　of　miniature　axial　blood　pump　has　achieved　required　pressure　and　blood　flow.　We　still　have　the　possibility　to　improve　the　blood　pump　by　reducing　energy　consumption　and　increasing　efficiency.　The　performance　test　and　comparison　in　simulative　circulation　apparatus　that　is　out　of　body　is　very　important　for　improvement　of　blood　pump.　It　can　accelerate　the　development　of　mechanical　assistant　therapy　and　increase　the　cure　rate　of　heart　failure　for　children.　©　2008　Springer-Verlag.