At 953K, anodic over voltage by electrolyzing LiCl and Li2CO3 were measured respectively by continuous pulse oscillograph method in a mixture fused salt of LiCl-LiF in a laboratory electrolyte cell and the change of polarization curve obtained was studied as well. According to kinetics of electrode process theory, we calculated and analyzed anode reaction mechanism and reaction rate-determining step. The results indicate that when over voltage entered into the Tafel zone with current density in range of 0.1 to 0.3A·cm-2, electrode reaction of LiCl is controlled by electrochemical polarization but electrode reaction of Li2CO3 is controlled by chemical polarization. With current density increase further beyond the Tafel zone (i>0.4A·cm-2), electrode reaction is changing gradually from dual control influenced by electrochemistry or chemistry united with concentration polarization to single concentration polarization. While electrolyzing Li2CO3, it is complexing oxygen ions discharging on carbon anode slowly that determine the whole electrode reaction rate.