The invention discloses an all-terrain vehicle braking system. The all-terrain vehicle braking system is composed of a hydraulic handbrake braking system and a hydraulic footbrake braking system. According to the improvement, brake cylinders of an existing hydraulic handbrake braking system of rear wheels are cancelled or brake cylinders of an existing hydraulic footbrake braking system are cancelled, three-way oil pipe joints are additionally arranged between the retained brake cylinders and brake oil pipes of the hydraulic handbrake braking system and the hydraulic footbrake braking system,first joints of the three-way oil pipe joints are connected with the brake cylinders, and second joints and third joints of the three-way oil pipe joints are correspondingly connected with the brake oil pipes of the hydraulic handbrake braking system and the hydraulic footbrake braking system. The all-terrain vehicle braking system has the advantages that rear wheel brakes of the hydraulic handbrake braking system and the hydraulic footbrake braking system can work separately and do not affect each other, in case of an emergency, the rear wheel brakes of the hydraulic handbrake braking systemand the hydraulic footbrake braking system do not interfere with each other in the state of a failure of the hydraulic handbrake braking system or the hydraulic footbrake braking system, and the safety of the all-terrain vehicle braking system is integrally improved.