The invention discloses a safety valve for a lead-acid storage battery of a motorcycle. The safety valve comprises a valve body and a bonnet; a valve hole is formed in the bonnet; a sealing ring is arranged at one end of the valve body; an external thread connected with the valve hole in a matched manner is arranged at the other end of the valve body; the external thread at one end of the valve body is screwed into the valve hole of the bonnet, and the sealing ring at the other end of the valve body is in interference fit connection with the bonnet; the sealing ring is made of a rubber material; and the rubber material is prepared from raw materials in parts by weight as follows: 70-90 parts of perfluoroether rubber, 30-40 parts of chloroprene rubber, 4-8 parts of a cross-linking agent, 2-4 parts of vaseline, 2-4 parts of coumarone resin, 4-6 parts of an adhesive toughening compound, 90-100 parts of a filler and 2-3 parts of an antioxidant DNP.