In order to study effect of laser scanning speed on the properties of final cladding layer in laser cladding repair process, Ni-based alloy cladding samples were prepared on QT500 nodular cast iron by laser cladding at different scanning speeds under the condition of synchronous powder feeding.The metallographic microscope of the cladding layer was observed by metallographic microscope, and the microhardness of the cladding layer was measured and analyzed by means of microhardness tester. The hardness, microstructure and sample dilution ratio of the cladding samples were obtained. The results show that the microstructure and properties of the cladding layer would be better with the increase of the laser scanning speed.The microstructure of the cladding layer is more compact and the average microhardness of the uniform cladding layer is improved significantly with the increase of the laser scanning speed. The optimal parameters are laser power of 1.9kW, scanning speed of 5mm/s, and the diameter of the spot of 4mm. The study provides the theoretical basis for reasonable selection of process parameters in laser cladding surface strengthening process.