Zero-voltage-switching(ZVS) is widely used to increase the efficiency of converters. It is influenced by some nonidealities, including the MOSFET’s junction capacitance and the dead-time. The buck converters may lose the ZVS operation when the junction capacitance incompletely charges or discharges during the dead-time. This paper aims to discuss the influence of nonlinear junction capacitance and dead-time on the ZVS region of buck converters and propose a method to get the boundary condition of ZVS, considering the interaction of these nonidealities. A 600V buck converter based on SiC MOSFET is built. The experimental results prove the correctness of the ZVS critical conditions with inductance and dead-time.