In view of an improvement of the fuel economy of extended range vehicle, a method based on the multi-island genetic algorithm has thus been proposed for an optimization of the operating point of the range extender. Firstly, the power parameters of the entire vehicle is matched to provide a foundation for simulation. Secondly, a five-point engine control strategy and braking energy recovery strategy are established, thus verifying the rationality of the model and parameter matching. Finally, the multi-island genetic algorithm is used to optimize the start-stop threshold of the range extender so as to improve the vehicle fuel economy. The simulation results show that after optimization, the fuel economy of the entire vehicle has been improved by 51.6% and 60.1% under WLTC and CLTC conditions respectively while ensuring the power performance, further enhancing the effective utilization of energy by the vehicle.