Disclosed is a self-destructing syringe, comprising an outer casing, a core bar, a piston, a conical head component, a syringe needle and a protecting jacket. The syringe needle is fixed in the conical head component, and the conical head component consists of a threaded conical head, a sealing ring, a transition part and a hollow wedge. The protecting jacket is put around the syringe needle and is movably connected to the needle base of the syringe needle; the conical head component is fixed in the inner cavity at the front end of the outer casing; the piston is installed on the core bar; the main part of the core bar is sheathed inside the outer casing; and the front end of the core bar is inserted into the conical head component and is able to make the syringe needle return inside the outer casing.