The invention discloses a method for demounting fixed cone lining plates of a breaker. The method includes the following steps that an upper frame body is cushioned to be higher through wood blocks; eight M36 bolts for fixing the fixed cone lining plates are demounted; ore between boom cross beams and the upper edges of the fixed cone lining plates is removed; two jacks are symmetrically clamped between the boom cross beams and the fixed cone lining plates, it is ensured that the bottoms of the jacks are placed in the middles of the upper edges of the fixed cone lining plates, the upper portions of the jacks eject the bottoms of the boom cross beams, and the jacks are kept balanced; the two jacks are manually operated, the ore between the fixed cone lining plates and the boom cross beams is knocked continuously so that the cleanliness of the contact faces between the jacks and the fixed cone lining plates and the contact faces between the jacks and the boom cross beams can be ensured, and the whole demounting process is completed until the fixed cone lining plates fall down. According to the method for demounting the fixed cone lining plates of the breaker, waste of manpower and material resources is reduced, the maintaining time is shortened, personal safety is ensured, and multiple purposes are achieved through the method.