Sulfur-containing species are suggested as the UV-absorbers in Venus’s atmosphere, which can be generated by photochemistry or electrochemistry. Here we report an electrical discharge experiment in gas mixtures of SO2 with CO2 and N2, under the pressure and temperature conditions relevant to the Venus cloud layer. We directly observed the primary breakdown products of SO2 as free radicals SO*, SI*, SII*, S2*, OI*, OII*; and the stable ending products as S8 particles and H2SO4 droplets. Their generations in minutes imply the formation of short-lived intermediate phases, including polysulfur and sulfur-oxides, as recognized candidates for the mysterious UV-absorber. The simultaneous occurrence of SO*and S2* under all experimental conditions indicates an equal probability for two major breakdown processes and their products. Compared with photochemistry, the high yields of reactive S-species from local electrochemistry would be responsible for the inhomogeneous distribution and temporal changes of dark strips in Venus UV images.