Control torque along geomagnetic vector could not be generated by magnetic rods when they are employed in momentum bias satellites with a pitch dipole moment. Stiffness control policy was developed to provide control torque by using magnetic rods to accelerate the motion of angular momentum vector along orbital normal. It made precession control vector move away from geomagnetic vector and move into location in favor of precession control. The expression of pitch dipole moment for stiffness control policy was developed by adding a stiffness term to classical control policy for momentum bias satellites on sun-synchronous orbit. Precession, nutation, stiffness feedback coefficient and their corresponding ratios were optimized and obtained via ant colony algorithm (ACA) and applied to numerical simulation. The comparison with the performance of the controllers with and without stiffness feedback coefficient indicates that stiffness control policy can improve precession control efficiency and increase pointing accuracy under persistent external disturbances.