Abstract: A safety syringe comprises a syringe body spaced by a spacer to be formed with a first receiving chamber and a second receiving chamber; and the spacer being installed with a first through hole; a control unit slidably matched to the second receiving chamber; and a front end of the control unit being installed with a second through hole; the base being connected to a front end of the control unit; and a push rod slidably moving in the first receiving chamber of the syringe body. Thereby, the syringe can be received in the second receiving chamber. When injection, the control unit and syringe are pushed to the second receiving chamber for moving forwards. After injection, the control unit is pushed so that the syringe is pulled into the second receiving chamber of the syringe body so as to prevent from hurting anyone.