Abstract: The matte-launder system of the slag cleaning electric furnace was retrofitted successfully in Guixi Smeltery in 1998. Its length was shorten from 7.5m to 3.1m and its horizontal inclination was enlarged from 7°25'to12°. More than two years smelting practice had proved that the modification solved a lot of problems such as heavy smoke, over-consumed graphite launder and higher solid matte rate due to over-long launder. As a result, the operation environment had been significantly improved and the maintenance cost had been decreased as well as the energy utilization factor had been increased.