An automatic jet injector for administering tissue is provided with a housing including a grip and a pushbutton； a syringe positioning device on a top of the housing and including an intermediate support and a rear pushing board having a lower through hole and a threaded hole under the through hole； a power source in the housing and including a power supply configured to supply power to the power source by pressing the pushbutton； a fastening member in the housing and being adjacent to a rear end of the housing； a positioning member being adjacent to the power source； a reciprocating screw having a front end operatively connected to the power source and a rear end fastened in the fastening member； a rod having a front end fastened in the positioning member and a rear end fastened in the fastening member； and a control device.
