The attitude motion characteristic of the bias-momentum satellite at the rate damping stage is analyzed, and a method for selecting weak bias angular momentum is proposed based on time-domain analysis to improve the dynamic performance of roll-yaw convergence. Considering the multi-star launching mode, the limitation of the installation constraints leads to the serious deviation of the bias angular momentum from the normal direction of the orbit after the separation, therefore, an attitude control method based on weak bias angular momentum is proposed. The method can avoid the problem that the convergent time of the roll-yaw angle is longer due to the gyroscopic intertia of bias angular momentum. The simulation results show that the proposed method can effectively reduce the attitude acquisition time and is easy to be implemented in engineering.