A deterministic computational model of high-temperature heterogeneous re- action between metal and oxide melts has been developed. Transport of reagents and products of reaction occur simultaneously both by diusion and by laminar natural con- vection of the melting metal and oxide uxes. The convection-diusion equations have been numerically solved by a nite-dierences time-implicit discretization scheme. The model was implemented by program which had been written in C# language. The com- putations have been performed for desulfurization reaction between liquid steel and slag phases.The computed results agree well with the results which were found by experimen- tal methods.