In this paper,a computational model is constructed to investigate the phenomenon of the initial plasma formation and current transfer in the single-wire electrical explosion in a vacuum.The process of the single-wire electrical explosion is divided into four stages.Stage Ⅰ:the wire is in solid state.Stage Ⅱ:the melting stage.Stage Ⅲ:the wire melts completely and the initial plasma forms.Stage ⅣV:the core and corona expand separately.The thermodynamic calculation is applied before the wire melts completely in stages Ⅰ and Ⅱ.In stage Ⅲ,a one-dimensional magnetohydrodynamics model comes into play until the instant when the voltage collapse occurs.The temperature,density,and velocity,which are derived from the magnetohydrodynamics calculation,are averaged over the distribution area.The averaged parameters are taken as the initial conditions for stage ⅣV in which a simplified magnetohydrodynamics model is applied.A wide-range semi-empirical equation of state,which is established based on the Thomas-Fermi-Kirzhnits model,is constructed to describe the phase transition from solid state to plasma state.The initial plasma formation and the phenomenon of current transfer in the electrical explosion of aluminum wire are investigated using the computational model.Experiments of electrical explosion of aluminum wires are carried out to verify this model.Simulation results are also compared with experimental results of the electrical explosion of copper wire.