A syringe includes a needle, a barrel and a push rod inserted in the barrel. The needle includes a needle seat, a stop ring fitted on an outer wall of the needle seat, and a check groove formed on the inner wall of the needle seat. The check groove is adapted to engage with a check rib on a core post of the push rod. A resilient plug is provided in the barrel. The resilient plug has a central through hole for insertion of the core post of a push head of the push rod. The push rod has a frangible point at a front end thereof. When the push rod is pulled backward, the needle is received in the barrel completely and the rear section of the push rod can be broken.
