In order to study the effect of laser shock on microstructure of the repair layer of E690 high strength steel by laser cladding， a special metal powder was selected to perform laser cladding on ready-made pits of E690 high strength steel， and the laser cladded layer was subjected to surface mechanical strengthening treatment by laser shock processing. The microstructure and surface residual stress of the repair layer were characterized by a scanning electron microscope， transmission electron microscope and X-ray stress analyzer. The results show that， after laser cladding repair， the repair layer presents an equiaxed grain structure. There is a good metallurgical bond between the laser cladded layer and the substrate. The residual stress on the surface of the repair layer is in a state of compressive stress. Following the laser shock processing， the cross-sectional grains on the repair layer are refined and a large number of deformation twins are observed. Coarse grains of the cladded layer are separated by parallel twin boundaries， which plays an important role in grain refinement process of the laser cladded layer. The dislocations on the surface of the sample experienced a slip on the ｛110｝ slip surface， forming dislocation entanglements around the grain boundaries. After laser shock， the value of surface residual compressive stress of laser cladded layer increases by 1.1 times compared with that prior to the laser shock processing.