Recirculating ball steering gear is one of the most widely used structural types at home and abroad. Generally, there are two-stage transmission pairs. The first stage is the screw nut transmission pair, and the second stage is the rack tooth fan transmission pair. In order to reduce the friction between the steering screw and the steering nut, the threads of the two are not in direct contact, and a plurality of steel balls are mounted therebetween to achieve rolling friction. Both the steering screw and the nut are machined with an approximately semi-circular spiral groove having a cross-sectional profile of two or three different arcs of a circle. The spiral grooves of the two can cooperate to form a spiral tubular passage of approximately circular cross section. There are two pairs of through holes on the side of the nut to insert the steel ball from the hole into the spiral passage. There are two steel ball guides outside the steering nut, and the two ends of each pipe are respectively inserted into a pair of through holes on the side of the nut. The inside of the duct is also filled with steel balls. Thus, the spiral conduits in the two conduits and nuts are combined into two separate closed steel ball "flow channels". When the steering screw rotates, the force is transmitted to the steering nut through the steel ball, and the nut moves in the axial direction. At the same time, under the action of the friction between the screw and the nut and the steel ball, all the steel balls roll in the spiral tubular passage to form a "ball flow". When the steering gear is in operation, the two rows of steel balls circulate only in their respective closed flow passages and do not come out.