A falling-prevention device for a clamping ring of an oil stop cover of a clutch comprises the clamping ring, a fixing plate and a countersunk bolt, wherein the fixing plate is a section of annular plate, and the inner edges of the left and right ends of the fixing plate extend outwards to form a left extending part and a right extending part; the diameters of the outer side surfaces of the left extending part and the right extending part are smaller than the diameter of an inner circle of the clamping ring; the left extending part and the right extending part extend to the positions below the left and right ends of the clamping ring correspondingly; and a countersunk bolt hole is formed in the middle of the fixing plate, and the countersunk bolt penetrates through the countersunk bolt hole and then is screwed in a bolt hole in the oil stop cover of the clutch. The left and right ends of the clamping ring are both inclined surfaces with the consistent inclination direction. The left and right ends of the fixing plate are provided with inclined surfaces matched with the inclined surfaces at the left and right ends of the clamping ring. The falling-prevention device has the beneficial effects that the situation that the clamping ring falls off the inside of a clamping ring groove, and then mutual staggered movement occurs between the clamping ring and the oil stop cover of the clutch can be effectively prevented, and thus the reliability of an automobile transmission can be effectively improved. The falling-prevention device has the advantages of being reasonable in structure and convenient to machine, manufacture and use.