Abstract: The flying-wing configuration boasts superior aerodynamic and stealth performance, yet the tailless design poses significant challenges to yaw control. The embedded drag rudder, by generating asymmetric drag, can provide a substantial yaw control moment for flying-wing aircraft. For an independently designed flying-wing configuration with a medium aspect ratio (4.58), numerical simulation was employed to investigate the effects of spanwise, chordwise, and normal position parameters of the drag rudder (deflected by 20°) on rudder efficiency and three-axis moment coupling effects under the inflow conditions of Mach number Ma = 0.6 and Reynolds number Re = 7.0×10⁶. The yaw control effectiveness and flow mechanism at different position parameters of the drag rudder were analyzed. The research results indicate that, in the spanwise direction, the closer the drag rudder is to the fuselage symmetry plane, the larger the spanwise extent of the pressure disturbance region on the wing surface, leading to more pronounced asymmetric drag. In the chordwise direction, the closer the drag rudder is to the wing leading edge, the larger the chordwise extent of the pressure disturbance region, resulting in more significant asymmetric drag and enhanced yaw control effectiveness. In the normal direction, the asymmetric drag generated by drag rudders at different positions is comparable; however, the farther the control surface is from the wing surface, the closer the starting point of the separated vortex behind it is to the wing trailing edge, which increases the lateral force difference and enhances yaw control effectiveness. Under the same control surface area condition, the maximum differences in yaw control efficiency generated by drag rudders at different spanwise, chordwise, and normal positions are approximately 20%, 200%, and 10%, respectively. Under the same cost of three-axis moment coupling effect, a drag rudder positioned close to the wingtip in the spanwise direction, near the leading edge in the chordwise direction, and at a certain distance in the normal direction can achieve stronger yaw control capability. This research can provide theoretical and technical references for the design of directional control schemes for medium aspect ratio flying-wing aircraft.