Motor dump trucks are important construction vehicles in open mine. The complexity of the open mine road requires a high quality steering system for the motor dump truck. Focusing on the 220 t load motor dump truck, the steering loads of the motor dump truck were analyzed and the main parameters of the full hydraulic system were calculated. Based on these, the parameters of steering cylinder, steering unit, flow amplifier, steering pump and steering accumulator were calculated. Finally the hydraulic schematics and the hydraulic component layout of the full hydraulic system were given.