Based on the experiments of laser-arc double-sided welding (LADSW) for a 4-mm thick stainless steel, the effects of laser power and arc current on weld cross-section, joint parameters and melting efficiency are mainly discussed. The results show that the weld cross-section of LADSW takes on the combination of typical weld profiles of laser welding and arc welding at lower heat input, while the combination characteristics doesn′t exist at higher heat input. The weld width at laser side increases with the increasing of laser power, whereas the weld width at arc side decreases at some extent. The increase of arc current can contribute to the increase of weld with at the arc side, but it doesn′t have much effect on the weld width at the laser side. The minimal weld width increases with the increase of both the laser power and arc current. The weld depth from minimal weld width to the laser side increases with the increase of the laser power, while decreases with the increase of the arc current. In the lack of penetration joint, the effect of the laser power on melting efficiency of arc welding is envident, while the effect of arc current on melting efficiency of the laser welding is little. In the full penetration joint, the melting efficiency of LADSW increases with the increase of both the laser power and arc current.