Active collision avoidance can assist drivers to avoid longitudinal collision through active brake. Regenerative braking can improve the driving range and braking response speed. At this stage, conventional hydraulic braking system limits the implements of above technologies because of its poor performance of response speed and coordinated control. While the brake-by-wire system is a better actuator that can fulfill requirements of automotive electric and intelligent development due to its rapid response and flexible adjustment. However, the system control algorithm becomes more complicated with introduction of regenerative braking and active collision avoidance function, which is also the main problem solved in this paper. First, a new type of cooperative regenerative auxiliary braking system (CRABS) of intelligent electric vehicles, which integrates the functions of brake-by-wire, regenerative braking and active collision avoidance, is proposed, for purpose of analyzing the improvement of active collision avoidance performance after the introduction of regenerative braking. The design of the system focuses on the Electro Hydraulic Brake (EHB) unit, control strategy of active collision avoidance and brake force distribution. Then, modeling and simulation are done to validate the feasibility of the proposed system scheme. Based on the Autonomous Emergency Braking (AEB) test procedures of European New Car Assessment Programme(Euro-NCAP), the simulation analysis scheme is made including simulation process, simulation test conditions and evaluation indicators. Finally, the hardware-in-loop (HIL) test bench based on the real motor system is set up to validate the conclusion drawn in the simulation analysis. The results show that compared with the conventional hydraulic braking system, CRABS system proposed in this paper conducts faster in braking response and closer to the ideal braking distance, and the performance of active collision avoidance is improved.