The present invention relates to a safety mechanism for microneedle injection, which mainly comprises an outer cylinder unit and an inner cylinder unit, wherein the outer cylinder unit comprises an outer cylinder body, a microneedle component and a cover body, and the outer cylinder body has one end The closed end and the other end are open ends, the microneedle element is coupled to the outer side of the closed end of the outer cylinder body, and one or more holes corresponding to the microneedle element are disposed at the closed end of the outer cylinder body at the closed end of the outer cylinder body The inner surface is provided with a tubular protruding post with a medicament receiving chamber, the cover body is combined with the open end of the outer cylinder body, and a middle hole is arranged on the cover body, the inner cylinder unit comprises an inner cylinder body, a piston and a a hollow needle structure, the inner cylinder body has a closed end at one end and an open end at the other end, and the piston assembly is disposed at a closed end of the inner cylinder body, and a coaxial coaxial hole is disposed on the closed end of the inner cylinder body and the piston. The hollow needle structure is worn in the inner cylinder body, the front end of the inner cylinder body is combined into the tubular protruding column of the outer cylinder body, and the other end passes through the middle hole of the cover body, and the hollow needle structure comprises a hollow needle and a set. At the end of the hollow needle The supporting member and a sliding seat disposed on the middle portion of the hollow needle are formed with at least one annular groove on the sliding seat, and at the same time, the outer tubular body and the side surface of the inner cylindrical body are respectively provided with a long slot corresponding to each other through the one end portion. The pushing member having at least one convex portion is inserted by the long slot of the outer c
