The formation process of a compositional gradient mixture was studied to provide fundamental ideas for manufacturing functionally gradient materials, in which chloride reduced metallic particles were infiltrated within a ceramic packing. The experiment using nickel chloride and alumina packing proved that the mixtures formed well controlled compositional gradient profiles. The infiltration process was successively simulated with a filtration theory which allows the design of the optimal gradients. Attention has also been given to the control of designed gradients by using a multi-layer packing composed of different particle diameters. The mixing state of the mixture was evaluated with the quality of mixing derived by using information entropy theory. The mixing calculated from the nickel images observed under electron probe microanalysis proved that the infiltration method was able to fabricate compositional gradient mixtures with satisfactorily homogeneous mixing.