The utility model discloses a single cylinder wheel cylinder, including the pump body, roof, the pump body, interior brake block, outer brake piece parallel in proper order and lay, and two guide pillars pass the both ends of roof, the pump body, interior brake block and outer brake piece respectively in proper order, guide pillar and roof fixed connection, guide pillar and the pump body and interior brake block clearance fit, guide pillar and outer brake piece fixed connection, leave the interval between interior brake block and the outer brake piece, the pump body forms a piston passage bore, and piston passage bore parallels with the guide pillar, piston passage bore two pistons of packing into, and the interval is left to two pistons inner relative, inlet port and air vent have been seted up to the pump body, and inlet port, air vent all link up with the piston passage bore of the pump body mutually, brake block in the outer terminal surface rigid coupling of one of them piston, the outer terminal surface rigid coupling roof of another piston, perhaps, spring in each overcoat of two guide pillars, push up in interior brake block and outer brake piece at the spring both ends, and the outer terminal surface and the interior brake block of one of them piston paste mutually, and the outer terminal surface and the roof of another piston paste mutually.