Laser micromelting repairing by laser cladding is a promising method for repairing difficult-to-weld materials. In this paper, Inconel 100 is used as the substrate and Inconel 718 is served as the filling powders to perform cladding repairs with no cracks under different laser powers (P) and scanning speeds (V). At present, the morphology of the repaired layer, the cause of crack formation, microstructure, and microhardness are studied, and the thermal-structure simulation is also conducted. The results show that the reason for crack formation is related to temperature gradient, cooling rate, thermal stress, and precipitates around the crack, and the microstructure also presents a large number of dendrites at this time. The precipitates in the repaired layer represent a typical phenomenon of segregation. The microhardness of the crack-free repaired layer decreases with the increase in V, up to 335HV0.1.