The invention discloses a consumable electrode mixed gas shielded arc welding process for steel plates with the thickness being 6-8 mm. The process is characterized in that the process includes the first step that a groove is formed in the surface of each steel plate; the second step that impurities on the surface and in the groove of each steel plate to be welded are eliminated, each welding face is wiped with sulfuric acid with the concentration being 0.5 mol/L, then each welding face is wiped with acetone after washed with water, and each welding face is naturally aired; the third step that the steel plates are horizontally arranged in a butt joint mode, the gap between the grooves is 1-2 mm, and preheating is performed on the steel plates after being fixed through a fixing device; the fourth step that consumable electrode mixed gas shielded arc welding is adopted, and welding process parameters are adjusted; the fifth step that during welding, pulse current is adopted for welding, multi-layer and multi-stage continuous welding is adopted, the interlayer temperature is controlled to be less than 210 DEG C, and shielding gas is still supplied for 3-4 min after welding is completed. The process is convenient to implement and high in welding efficiency; the mixed gas shielded arc welding is a conventional welding method, equipment and consumables can be purchased easily, and welding workers can master and implement the process easily; an automatic welding process can be adopted, the welding efficiency is high, and the occurrence rate of welding defects is low.