The invention discloses a limit protection device for a supporting oil cylinder of an open type whole-section tunnel rock boring machine. The limit protection device comprises a base frame and a supporting oil cylinder arranged on the base frame, and is characterized in that a groove is arranged on the base frame; one end of the supporting oil cylinder is a restrained end which is movably arranged in the groove of the base frame; the other end of the supporting oil cylinder is a stressed end which is connected with a thrust oil cylinder by a supporting shoe; the groove wall of the base frame is provided with a convex elastic part which corresponds to the side wall of the restrained end of the supporting oil cylinder. The limit protection device has simple structure and low cost; when the supporting oil cylinder bears large lateral pushing force from the thrust oil cylinder through the limit protection device, elastic function of the elastic component in the limit protection device balances the pushing force, so that bending deformation of one end opposite to the other end bearing the lateral force of the supporting oil cylinder is reduced, excessive damages are avoided; when the lateral force is relieved, the supporting oil cylinder can be protected to return a normal working position.