Abstract: Seam explosive welding was used to bond aluminium plates and steel plates with groove.The bonding interface of explosive welded aluminium-steel plates were analyzed by means of metallographic microscopy and scanning electronic microscope, which the joints around grooves were good.In the bonding zone of groove, transition-layers and melting-lumps could be seen clearly and metallic atomic diffusion exist in transition-layers.Melting-lumps are made by metallic plastic deformed heat when explosived welding, transition-layers are actually metallic plastic deformed layers.Plastic deformation, high temperature and melt, atomic diffusion are necessary condition of explosive welding.Results show that the technics of seam explosive welding with groove can be an importmant complementarity to explosive welding used in repairs and are potentially useful.