The present invention relates to a safety syringe automatic retraction structure and an operation method thereof, wherein the outer plunger rod is sunk into the bottom of the outer cylinder, and the inner plunger rod is sunk into the outer plunger rod and immediately behind the pulling member, and the resilient tappet disposed in the inner plunger rod will protrude out to the chute of the outer plunger rod and abuttingly contact with the inner wall of the outer cylinder, and then pulling the outer plunger rod when the drug solution is extracted, the resilient tappet of the inner plunger rod moves up to lockingly engage with the end chamber of the outer cylinder during the injection, the outer plunger rod is pushed, while the inner plunger rod remaining still, until the pulling member at the front end of the outer plunger rod lockingly engages with the taper slot of the needle, at this time an vacuum sealed chamber is formed behind the pulling member of the outer plunger rod continue to press down the outer plunger rod and the pulling member will be retracted due to the reaction force and as the straining force of the pulling member becomes small, the pulling member and the needle together are sucked into the vacuum sealed chamber due to external atmospheric pressure, enabling the needle to retract inside the outer cylinder for discard so as to achieve the efficacy of convenience and enhanced security.
