A novel rigid mechanical locking mechanism and a locking or unlocking method are provided. The invention belongs to the technical field of space optical remote sensing instruments, and designs a novelrigid mechanical locking mechanism in view of the specific demand of the scanning mechanism of the camera. The novel rigid mechanical locking mechanism designed by the invention is assembled on the two sides of a shafting of a scanning mechanism, and can lock or unlock the shafting of the scanning mechanism at any time under an instruction sent by a controller. The shafting of the scanning mechanism is rigidly locked before the launch of a satellite. In the launch stage, the vibration overload of the shafting is borne by the rigid mechanical locking mechanism. The support elements of the shafting are protected by the high support rigidity of the rigid mechanical locking mechanism. The locking operation precision and the locking/unlocking position feedback precision are realized by optimizing the speed reduction ratio of a speed reduction component to a first linear motion pair and the speed reduction ratio of a speed increase component to a second linear motion pair. High support rigidity is realized through the design of the installation arrangement mode and the pre-tightening force of a linear support pair. A locking pin with large taper angle is adopted, which ensures that self-locking will not occur after locking.