This brief paper focuses on longitudinal force distribution on a four-wheel-independent-drive electric vehicle for improving yaw stability performance. A longitudinal force control allocation method based on differential driving and differential braking is presented in this paper. A hierarchical coordinated control strategy is developed. The upper controller is designed to determine the generalized moment required to keep vehicle in stability region. The lower controller is designed to distribute braking force or driving force according to objective optimizing torque distribution function. Considering problem of faulty motors, concept of faulty factor is applied on the coordinated control strategy, enabling the redistribution of objective torque in remaining normal motors, and the problem of the motor failure control is solved. Results of computer simulation show that the proposed control method could improve electric vehicle yaw stability during a critical maneuver.