Abstract: Cobalt-based alloy layer was prepared on the surface of 32Cr3Mo1V cast rolling sleeve by ultra-high speed laser cladding. The effects of laser power, cladding rate and powder feeding rate on the forming quality of the cladding layer were analyzed by single factor method. Combined with the actual working conditions of the cast rolling sleeve, the thickness and microhardness of the fusion layer were determined as the investigation objects. The optimal process parameters were determined by orthogonal test, and the cladding layer prepared by the optimized parameters was analyzed by scanning electron microscope. The results show that within a certain range of parameters, the thickness of the cladding layer increases with the increase of the powder feeding rate and decreases with the increase of the cladding rate, and it has no obvious correlation with laser power. The optimized parameters are laser power of 2500 W, cladding rate of 15 m /min and powder feeding rate of 30 g/min. The microstructure of the fusion coating prepared by this process is very uniform and fine, and there is an obvious arching delamination phenomenon. The bottom and middle regions of the fusion coating are mostly columnar crystals perpendicular to the fusion line of the fusion layer/substrate interface or overlap fusion line. The growth direction has high consistency. The growth direction of dendrites at the top of the fusion layer is relatively disordered. The microhardness of the fusion layer is significantly higher than that of the substrate, which is beneficial to improve the wear resistance of the cast rolling sleeve.