The invention discloses an expansion sheet of a pressing device for grinding wheel firing. The pressing device for grinding wheel firing comprises a tray, a supporting rod, a pressing disk, a spring and a lock nut. The supporting rod is arranged on the tray. One end of the supporting rod is welded to the center of the tray. The other end of the supporting rod is provided with a thread structure. The pressing disk is mounted on the supporting rod in a penetration mode. The spring is arranged on the portion, between the lock nut and the pressing disk, of the supporting rod. The lock nut is arranged on the supporting rod and connected with the thread structure. The expansion sheet is arranged between a groove and a movable bar. The expansion sheet is arranged in the height direction of the groove. The expansion sheet is of a wavy structure. The width of the expansion sheet is less than or equal to that of the groove. The expansion sheet is arranged between the movable bar and the groove to increase acting force between the moving bar and the groove, so that the movable bar abuts against a grinding wheel to achieve the better pressing effect.