Results of numerical simulations of the melting wave in a tungsten wire heated by a high-power nanosecond current pulse are presented. To take into account the hydrodynamic effects under melting, a semiempirical multiphase equation of state for tungsten is used. The structure of the melting wave at different parameters of the heating is studied, and a theoretical evaluation for the thickness of this wave, δ m , is proposed. The homogeneity of the distribution of parameters over the wire can be expected in the case of δ m a 0 , where a 0 is the initial radius of the wire. The melting wave can be considered as a discontinuity of thermophysical properties of the solid and liquid phases at δ m a 0 .