A safety syringe includes a barrel 2, a plunger 3, and a needle hub 4. The barrel 2 is extended axially and includes a first tube portion 21, a second tube portion 22 extended from an end of the first tube portion 21, and a first folded ring 23 flexibly branched and formed on an inner side of the first tube portion 21 and disposed around the axis, such that after the first folded ring 23 is unfolded, the first folded ring 23 is bounded and extended from the first tube portion 21 towards the second tube portion 22, and includes a first ring base portion 231 disposed at the first tube portion 21 and a first flexible portion 232 movably disposed opposite to the first ring base portion 231. The plunger 3 includes a rod 31 and a plug 32 installed at an end of the rod 31. The needle hub 4 is detachably installed in the second tube portion 22. The plunger 3 can be moved to an injecting position, a limit position, and a disposal position with respect to the needle hub 4.
