Reversable safety syringes

A pull-back type safety syringe comprises a needle cylinder which is provided with a containing hole, a needle stand which can be arranged in the containing hole of the needle cylinder by control, limitation and sliding and is provided with an insertion hole which passes through from the end surface and an infusion hole which is led to a needle, a pushing rod which is provided with a rod body, an insertion rod and at least one torsion block which is arranged on the insertion rod and can be inserted in the insertion hole of the needle stand; therefore, when the pushing rod is pushed, the insertion rod is inserted in the insertion hole of the needle stand, so the utility model can not have the blocking function; when the pushing rod is pulled back, the torsion block is turned by the blocking of the inner wall of the insertion hole of the needle stand, so the needle stand and needle head can be pulled back to the interior of the containing hole of the needle cylinder.