Films with gradient pores (gradient layer) were prepared on rough-pore substrate materials by centrifugal deposition process. The relationship between the filtration performance of the composites and the particle size as well as the thickness of gradient layers was investigated. Results show the particle size of gradient layers should be less than the mean flow pore size of substrate materials so as to obtain the optimum filtration performance. With the thickness of gradient layers increasing, the permeability of the composites decreased while the filtration precision increased. There is optimum matching thickness of gradient layers for the optimum matching of the two performances, which has linear relation with the particle size of gradient layers, and the mean flow pore size of substrate materials is the intercept of the straight line.