The invention discloses an anti-theft lock cylinder with a direct plug-in key, comprising a lock cylinder seat body provided with a key slot, a bullet hole and bullets, wherein one end of the lock cylinder seat body close to the key slot is provided with a locking slot, the locking slot is internally provided with a locking shaft, the opposite end of the lock cylinder seat body is provided with alock cylinder hole, the lock cylinder hole is internally provided with a lock cylinder shaft, one end of the lock cylinder shaft is fixedly connected with a knob, and the opposite end of the lock cylinder shaft is connected with a locking dog; and the lock cylinder seat body is provided with a lock cylinder sheath, a locking bayonet blocks a locking shaft when the lock cylinder is in a locked state, and the inner end face of the lock cylinder sheath and one side of the lock cylinder shaft are fitted. By adopting the technical scheme in the invention, the problems that the lock cylinder technical principle and mechanical structure of the traditional lock tool are single and the anti-theft performance is poor are solved, and a mechanical lock cylinder with a more reasonable, compacter and safer mechanical structure is provided for people.