The niobium carbide powder was prepared via electrochemical reduction of the mixture of Nb2O5 and carbon in molten CaCl2–NaCl. The reaction pathway from the sintered precursor to the final product has been investigated. The effect of the working temperature on the reduction of the Nb2O5/C composite precursor was considered. The role of carbon during the electrochemical reduction of the composite pellet was discussed. The samples were analysed by XRD and SEM. The results indicated that the NbC powder was approximately 200 nm after the reduction. Nb2O5 was gradually reduced to Nb, and NbC was subsequently obtained by the reaction of carbon with Nb metal. In addition, Nb2O5 could spontaneously react with CaO in the melt to form a serious of calcium niobates. The participation of carbon was available for the efficiency of electro-reduction of Nb2O5.