Abstract: This paper adopts an instantaneous optimization control strategy for a chargesustaining,parallel hybrid electrical vehicle (HEV) with the instantaneous fuel economy and emission as objective function,and this strategy sets the vehicle overall power conversion efficiency and engine emission "efficiency" as the guideline of fuel consumption and emission.Based on the math models related to the entire vehicle and its powertrain,a Matlab/Simulink simulation platform is built up to search the ideal operating point of the vehicle's engine and motor by the objective function optimization under HEV's possible speed-torque sets and the corresponding gearshifts,which are then stored in the HEV's onboard supervisory controller.Data are looked up from the maps by the controller based on the instantaneous driving condition,and are simply but properly modified according to the preset charge-sustaining requirement.Validity and real-time responsibility of this control strategy are proved by simulations with several typical driving cycles and other kind of vehicle simulation software,revealing good practicability of the strategy.