A safety syringe (20) is disclosed. Several elastic support elements (213) are disposed in the hollow syringe body (21). A piston (223) is mounted on one side of a plunger (22). A first hitch element (222) is protrudly disposed on the piston (223). The plunger (22) end with piston could enter the rear end (212) of the syringe body. The needle assembly (23) consists of a first needle seat (231), a second needle seat (232) and a needle (233), which are assembled each other. The needle assembly comprises a second hitch element (237). The elastic support elements against the bottom of the second needle seat (239) as the needle assembly is disposed on the front end (211) of the syringe body to provide a support force for the needle, so as to prevent the needle from being retracted when injecting. After an injection, the first hitch element moves into the second hitch element, the needle assembly is pulled back by the plunger so that the needle is receded into the syringe body. The safety syringe is non-reusable, hence indirect infection could be avoided.
