Directing against the real working condition of Cr-plated gun bore, the laser-quenching of substrate was adopted. It was indicated by multi-cracks tensile method that the interfacial shear strength was greatly increased, its service life could be obviously improved, and the mechanism was discussed from the materials science. The interfacial strength was evaluated by ion peening technology ,the result showed that laser quenching substrate could not only eliminate interlayer between substrate and Cr-coating but also increase the strength of materials near interface. The mechanism of improving strength was due to the refined grain of Cr-coatings interface.