A kind of disposable safety self-breaking injector that steel needle can be safely retracted in injection tube using Hou, including a core bar, an injection tube, a piston, a needle stand, a self-destruction part and a steel needle, wherein the self-destruction part connects the steel needle, the core bar top is equipped with a piston deck, the piston deck is equipped with groove, along snap ring is equipped in the groove, which is equipped with the groove on conehead and piston deck and cooperates； Its characteristic is in what: the axial cross section of groove is triangle.一種使用後能將鋼針安全地拉回注射筒內的一次性安全自毀注射器，包括一芯桿、一注射筒、一活塞、一針座、一自毀件及一鋼針，其中該自毀件連接該鋼針，該芯桿頂端設有一活塞卡座，該活塞卡座設有凹槽，該凹槽內沿設有卡環，該自毀件下部設有錐頭與活塞卡座上的凹槽配合；其特徵在於：凹槽的軸向截面為三角形。
