Abstract: The rotary steering drilling technique has become an indispensable core technology in the present drilling operations. In this paper, a mechanical model was built according to the principle of static push-the-bit rotary steering control and in conjunction with the actual need of drilling engineering. According to the principle of maximum supporting claw force in the favorable area and minimum supporting claw force in the unfavorable force, this paper presents two control schemes: dividing the area by 120° and 60°. While optimizing the mathematical model, the stress on each supporting claw is decomposed to the bias resultant force direction and to the direction perpendicular to the bias resultant force. Using mechanics vector analytic method, a mechanic equation is built under different bias resultant vector, and then solves the related equation to find the stress expressions of each supporting claw at different areas. This paper analyzes the stress changes of each supporting claw at different areas, compares the changing trend and optimizes the more steady control scheme so as to increase the service life of the instruments, reduce drilling accidents and reduce drilling costs.