Seat post anti-theft structure and bicycle

The utility model provides a seat post anti-theft structure and a bicycle. The seat post anti-theft structure is arranged in a middle tube of the bicycle and comprises a seat post and a seat post clamp, the seat post is movably inserted into the middle tube and comprises a limiting groove, and the seat post clamp comprises a retaining ring, a radial through hole, an elastic positioning piece and an anti-theft screw piece. One end of the middle pipe is sleeved with the retaining ring, the radial through hole is located in the retaining ring and correspondingly communicated with the hole of the middle pipe, and the elastic positioning piece is movably contained in the radial through hole and protrudes into the hole; and the anti-theft screw piece is locked in the radial through hole to limit the elastic positioning piece in the radial through hole. When the seat rod moves towards one end in the axial direction relative to the middle pipe, the elastic positioning piece abuts against the limiting groove and is li