A kind of improvement of remaining needle of this case system,It includes a delivery conduit,One relay pipe,One extension tube attached and a transfusion catheter； The soft needle section of one tapered portion of a stretching what is axially arranged in front of the delivery conduit,And the relay pipe both ends are respectively and fixedly connected between the what tapered portion and the extension tube attached,And the extension tube attached Hou section outer surface is equipped with a male threaded section,Wherein the adjacent what extension tube attached one end of the transfusion catheter is equipped with one first connector,There is first connector inside to connect ring equipped with negative thread section,So as to the male threaded section for the what extension tube attached Hou section that is spirally connected,So that the transfusion catheter fixed what extension tube attached Hou section.本案係一種留置針之改良，其包括一輸送導管，一中繼管，一外接管及一輸液導管；該輸送導管前方軸向設有一伸出於一錐形部之軟質針段，而該中繼管兩端分別固接於該錐形部及該外接管之間，且該外接管後段外表面設有一陽螺紋段，其中該輸液導管鄰接於該外接管一端設有一第一連接件，該第一連接件具有一內部設有陰螺紋段之接環，以便螺接於該外接管後段之陽螺紋段，使得該輸液導管固設於該外接管後段。
