Abstract: A power steering system for construction equipment is disclosed. In the steering system, a plurality of internal passages are selectively formed in the directional control valve for left and right steering cylinders. The internal passages thus selectively allow pressurized oil to be fed from an oil pump into both the large chamber of the right cylinder and the small chamber of the left cylinder with a reversible motor starting by pressurized oil discharged from the other chambers of the two cylinders in the event of rotating the steering wheel to the left. The internal passages also allow the pressurized oil to be fed into both the small chamber of the right cylinder and the large chamber of the left cylinder so that the motor is started by pressurized oil discharged from the other chambers of the two cylinders when the steering wheel rotates to the right.