The rise of quality metal yield is governed by rate of mass transfer of metal ions through molten electrolyte from near the anode to near the cathode space. The most essential factors, influencing on mass transfer kinetics upon electrorefining the heavy nonferrous metals is fused salts, are defined. A procedure for determining the values of mass transfer coefficient directly in the process of electrorefining from electrode polarization value, steady at certain current density, is used in definition of above factors. The mass transfer kinetics upon Pb electrorefining is studied.