Abstract: An database was developed to for filling the robot welding moderate-thick plate with variable groove, based on laser sensor scanning and fitting the section area. The welding section area corresponding to different welding parameters as variables was saved and the least square method was applied to deduce the relationship between the welding area and the welding speed. The system based on thef groove cross-section variation and changes of adaptive control welding speed could fill the workpiece well and solve the problem of welding parameter adjustment on variable groove. It could also use the database language to standardize the management of the knowledge base, and constantly improve the welding database. Taking a 12 mm thick variable groove of moderate-thick plate as a test, the result showed that the welding effect is good and error of groove metal filling volume is small.