Abstract: The electrochemical reduction of C₂H₂ to C₂H₄ in 0.1M NaClO₄ DMF solution containing FeCl₂ and K₂MoS₄ has been investigated by using potentiostatic electrolysis, cyclic voltammetry and a.c.impedance methods. The results showed that the ferrous-molybdate systems exhibited an appreciable electrocatalytic activity and high selectivity in reducing C₂H₂ to C₂H₄ when the potential of the graphite electrode was at -1.50V (vs.SCE). It was sugges-ted that the reaction Mo(Ⅵ)→Mo(Ⅴ) takes place at -0.5--1.0V and the reaction Mo(Ⅴ) to Mo(Ⅲ) at -1.0--1.5V,which proceeds through a consecutive electron transfer mechanism, forming a complex of Mo(Ⅲ) as electorcatalytically active species, faciliating the electron transfer of the reaction.