With the rapid development of LED industry, its share in the automotive lighting market is also growing very fast year by year. At present, there are mainly two design methods of LED-based headlamp which are single-moduled and multi-moduled, what′s more, most of the headlamp system are composed of several modules which can just be used by specific cars. This kind of headlamp system has large volume, high power consumption, high cost and narrow application range. The main research of the article was the optical design method of the single-moduled LED headlamp with small volume and outstanding lighting effect. A brand-new design method of LED-based integrated headlamp optical system was proposed, which used only one group of reflectors and one LED module to meet the lighting needs of high beam and low beam using a baffle. The final design method was determined through software simulation and contrast of different design methods to pick up a best one. Finally, it puts forward a new design method of LED-based integrated headlamp system with high efficiency, small volume and excellent lighting effect which can be used by different kinds of cars.