This invention relates to a syringe with a blocking structure, having a flexible blocking piece extended from the rod body outwardly. The flexible blocking piece is bent along the direction of the rod body entering into the barrel. A flange is protruded relatively inside the outer diameter of the flexible blocking piece. When the rod body is pushed forward into the barrel and the flexible blocking piece is in contact with the flange, the flexible blocking piece is bent along the bending direction thereof to pass through the flange, enabling the rod body to enter into the barrel when the rod body is pulled backward toward the barrel and the flexible blocking piece is in contact with the flange again, the flexible blocking piece is reversely blocked by the flange relative to the bending direction thereof, so as to constitute this invention.一種具有阻擋結構的針筒,具撓性擋片自桿體向外延伸,撓性擋片彎折方向順著桿體進入筒體內的方向,凸緣相對凸出於此撓性擋片之外徑內,桿體往筒體內朝前推入至撓性擋片接觸凸緣時,撓性擋片順著其彎折方向彎折而穿過凸緣,令桿體能進入筒體內;另桿體往筒體朝後拉出且撓性擋片再接觸凸緣時,撓性擋片相對其彎折方向以逆向阻擋於凸緣,藉此構成本創作。2‧‧‧筒體21‧‧‧筒身211‧‧‧前端212‧‧‧後端213‧‧‧前定位座214‧‧‧筒身倒勾片215‧‧‧凹槽22‧‧‧針頭座221‧‧‧頭座段222‧‧‧套合段23‧‧‧凸緣24‧‧‧凸緣3‧‧‧注射針4‧‧‧桿體41‧‧‧推送端42‧‧‧桿身段421‧‧‧環型凸緣422‧‧‧活塞座43‧‧‧卡合段44‧‧‧頂桿段5‧‧‧撓性擋片6‧‧‧撓性擋片7‧‧‧活塞片
