In this paper, an LLC resonant converter design methodology for battery charger based on mode analysis is presented. The accuracy of DC gain curve obtained by mode analysis is much higher than that by FHA. Conduction loss and switching loss can be minimized by reasonably configuring charging trajectory on the mode distribution map. ZVS and ZCS can be realized during whole charging process. Finally, a 700W charger prototype with a peak efficiency of 96.1% was built to verify the effectiveness of design method.