Laser cladding was done on the 45 # steel substrate using an auto feeding powder method. Effect of scanning speed on the microstructure and solidification process of the laser cladd Ni alloy have been systematically studied. Experimental results show that the clad microstructure is composed of primary dendrite and block(or needle) eutectic. The mophology of eutectic carbide is resulted from its chemical composition. Bright ribbon does not exist, and there is finer hypoeutectic microstructure at the interface between overlapping and clad layers. The clad microstructure becomes finer and inhomgeneous with increasing the distance from the interface. The increase of scanning speed results in finer structure, higher micro hardness, and better homogeneity. The solidification process is discussed based on the analyzed model. Some solidification parameters of laser melting bath are also calculated.