The electrochemical behaviour of the silylene-phenylene, silylene-thienylene, silylene-diphenylene and silylene-anthranylene copolymers was investigated using cyclic voltammetry. The oxidation potentials of these organosilicon copolymers decreased with increasing dimethylsilylene chain length. The change of the oxidation potential was explained by considering the sigma-pi conjugation between the dimethylsilylene chain and the pi unit. The cyclic voltammograms of the organosilicon copolymers showed the characteristics of an irreversible system. The absorption spectra showed the degradation of the Si-Si chain of the organosilicon copolymers by electrochemical oxidation. The molecular orbitals were calculated to discuss the sigma-pi conjugation state and to identify the oxidation site in the polymer chain.