The utility model discloses a mechanical lock cylinder, which relates to the technical field of the manufacture of a lock. The mechanical lock cylinder comprises a lock cylinder body, an inner lock cylinder which is arranged in the lock cylinder body and a shifting block, wherein a key hole is formed in the inner lock cylinder, at least three locking pin slide-ways are formed in the inner lock cylinder, a locking pin is installed in each locking pin slide-way, and each locking pin is provided with a transverse tongue extending into the key hole; annular slide-ways corresponding to the locking pin slide-ways are formed in the inner wall of the lock cylinder body, the width of each annular slide-way is greater than that of the corresponding locking pin slide-way, when the inner lock cylinder stays at a lock state, the locking pin at the left side of the shifting block falls into the annular slide-way and is tightly fit to the right side wall of the annular slide-way, and the locking pin at the right side of the shifting block falls in to the annular slide-way and is tightly fit to the left side wall of the annular slide-way. The mechanical lock cylinder is fewer in components, high in antitheft performance, capable of realizing the installation with no clamping spring or clamping block, rapid and simple to dismount and install and capable of realizing the unlocking on two ends.