The invention provides a parking brake system of a dump truck. The parking brake system includes an energy accumulator, a parking brake valve, a parking brake oil cylinder, a parking brake, an oil tank, a filtering device, a hydraulic pump, a safe valve, a lifting reversing valve, a lifting oil cylinder, a hydraulic control air valve, a shuttle valve, a manual flameout switch, an air bag, a flameout air cylinder and an air-controlled hydraulic valve. The parking brake system of the dump truck is relatively high in safety performance.