The invention belongs to a manufacturing process for welded sandwich construction panels, and particularly relates to a manufacturing process for a welded sandwich construction panel with a porous panel core. The manufacturing process comprises the following steps that firstly, panels are manufactured by a metal plate, and the porous panel core is manufactured by porous core materials; secondly, the upper end and the lower end of the porous panel core are covered with the panels to obtain a sandwich construction panel semi-finished product; thirdly, the sandwich construction panel semi-finished product is fed into a brazing furnace with a conveying-flattening device and subjected to brazing, acting force is exerted on the panels at the moment of conveying and flattening in the brazing process, and the welded sandwich construction panel is obtained. The sandwich construction panel can be prevented from deforming in the brazing process, the contact stability of the panels and the porous panel core is further guaranteed, proceeding of the brazing process is facilitated, the quality of the obtained sandwich construction panel is good, and surface evenness is good.