The high efficiency multi-resonant converter(MRC) is capable of operating at a high frequency because the losses are decreased due to the resonant tank circuit. Such a few MHz high frequency applications provide high power density[W/inch3] of the converter. However, the resonant voltage stress across the switch of the resonant tank circuit is 4∼5 times input voltage. This high voltage stress increases the conduction losses because of on-resistance of a MOSFET with higher rating. In this paper, the modeling analysis for the AT Forward MRC suggested to solve the these problems is discusses. The operational modes of the AT Forward MRC are divided to 8 equivalent modes according to the two switching sequences. Each mode analysis is covered using the equivalent circuits modeled over all of the paper. The operational principle of the resonant converter was verified through the experimental converter with 48[V] input voltage, 5[V]/50[W] output voltage/power and PSpice simulation. The measured maximum voltage, 5[V]/50[W] output voltage/power and PSpice simulation. The measure maximum voltage stress is 170[V] of 2.9 times the input voltage and the maximum efficiency is measured to 81.66%.