Protection device for cylinder pin lock

The invention provides a protection device for a cylinder pin lock, which can perform a blocking action of a shutter by using a preloading force of a preloading unit, can promote the operability and can prevent the damage formed in the process of moving the shutter towards the blocking position. The protection device for a cylinder pin lock is provided with a shell, a shutter for blocking a key hole on the blocking position and opening the keyhole on an opening position, a locking unit for locking the shutter on the blocking position, an unlocking unit for unlocking the locking unit, a tensional spring for continuously preloading the blocking position of the shutter, a blocking projection for blocking the shutter on the opening position and a relieving unit for relieving the blocking, wherein the shutter is provided with a first resisting part and a second resisting part. When the blocking of the blocking projection is relieved, the shutter is resisted with a side wall of an igniting key.