“Soichiro Honda Cup, Honda Econo-Power Competition”, is an annual international energy-saving competition which is hosted by Honda Motor Co., Ltd. Till now it has been held 27 sessions. The aims of the EP project are: promoting the development of environmental protection, making full use of limit earth resources, challenging the fuel consumption limitation of vehicle. Tongji University's students' team has participated in the competition for seven consecutive times. In order to minimize the fuel consumption of the EP energy-saving vehicle, this paper focuses on the technical methods of improving the fuel economy of the engine. Firstly, the optimization of the carburetor. Secondly, for the purpose of improving combustion efficiency, researches on dual spark plug and compression ratio are done. Others, because of the specialty of the vehicle, which is operated mainly at a speed between 20km/h and 40km/h (average speed 25km/h), the structure of the engine is optimized, such as, intake manifold, air filter, transmission system, electrical generator and air-cooling fin. Each optimization measure has made a comparative test and analysis, and these technical methods above are remarkably effective.