The invention discloses an internal riveting mechanism. The mechanism comprises an upper die structure and a lower die structure, wherein the upper die structure comprises an upper die plate, outer guide sleeves are symmetrically arranged on the two sides below the upper die plate, pressing blocks are arranged in the middles of the outer guide sleeves, each pressing block is in a capital omega shape, the two ends of the capital omega shape of each pressing block are provided with locking sleeves, the lower die structure comprises a lower die plate, a lower ejection block is arranged in the middle of the lower die plate, the lower ejection block is embedded into the lower die plate, the lower part of the lower ejection block is connected with the lower die plate through a spring, side pushing blocks are arranged on the two sides of the lower ejection block, riveting heads are symmetrically arranged at the positions, opposite to the central axis of the lower ejection block, of the innerside faces of the side pushing blocks on the two sides, locking guide columns are arranged in the middles of the side pushing blocks on the two sides, outer guide columns matched with the outer guidesleeves are arranged above the side pushing blocks on the two sides, and side pushing air cylinders are arranged on the outer side surfaces of the side pushing blocks on the two sides. According to the mechanism, a riveting part with the riveting point at a sunken part of a product is riveted, the overall performance is high, the locking force is large, the structure is stable, popularization andapplication are facilitated.