The electrochemical behavior of 2,3,5,6-tetrachlorobenzoquinone in dimethyl sulphoxide with tetra-n-butylammonium perchlorate supporting electrolyte has been reported in this paper. The experimental results show that the increasing current is due to freezing of the solvent, DMSO, which will make the true concentration of 2,3,5,6-tetrachlorobenzoquinone higher in solution around the working electrode. It is shown that DMSO is a good solvent for solid electrochemical researches.