A safety syringe includes a barrel, a push rod, a driving module, and a needle mount. The barrel includes a hollow passage and a barrel cover, and the push rod includes a pad disposed around a distal portion and pushed tightly along the hollow passage of the barrel, and the barrel cover includes a plunger, a driving module of a piston pump, and a needle mount having a cut surface at the piston pump, such that the distal portion of the push rod pushes the plunger to move forward, while the cut surface of the distal portion and the cut surface of the needle mount are pressed to separate with each other, and the plunger continues moving forward to offset the air pressure therein, so as to retract the needle mount into a push rod accommodating cavity to accommodate the needle safely after an injection is taken place.