By taking 42CrMo alloy steel as the metal substrate and using (Ti-B4C) as the reactive system, the laminated composites of TiB2-based ceramic and 42CrMo alloy steel with the nano-structured gradient were achieved by centrifugal reactive casting processing. Based on XRD, FESEM, and HRTEM, it was considered that because of thermal explosion induced by centrifugal reactive casting processing, fusion-induced interdiffusion was initiated between the full-liquid ceramic and alloy steel, resulting in the formation of the intermediate liquid between the liquid ceramic and the steel substrate. Subsequently, the strong Stokes flow under high centrifugal force promoted the ceramic nuclei to collided with the others, thereby accelerating the coarsened ceramic particles to float up, meanwhile, the alloy-enriched liquid also flowed and converged toward the steel substrate. Finally, in the interlaminar region of the composite there developed nano-structured graded microstructure that the spatial size of ceramic/alloy phase boundary was continuously graded from the ceramic to the steel.