To improve the fuel economy of parallel hydraulic hybrid vehicles(PHHV) by operating the engine in the optimum efficiency range and making use of regenerative braking during deceleration,the design criteria of important components for PHHV were researched.Based on the analysis of braking characteristics of PHHV in the city drive cycle and the high power density of hydraulic transmission,a new regenerative braking strategy tailored specially for PHHV was proposed.Based on the Matlab/ Simulink software platform,the performance simulation was accomplished under a selected driving cycle.Results show that the parameters of propulsion system are reasonably matched;the proposed hydraulic regenerative braking strategy can reasonably distribute the hydraulic regenerative braking torque and traditional friction braking torque,which effectively regenerates braking energy of the vehicle under the premise of safe braking and improves the braking performance.