Nanometer copper (Cu)-doped poly-4-methyl-1-pentene (PMP) foam is prepared by thermally induced phase inversion and ultrasonic dispersal. The nanometer Cu powders are dispersed uniformly in the horizontal direction of the foam and sink a bit in the vertical direction. The practical concentration of Cu atoms in the foams is lower than the theoretical concentration. Experiments reveal that a higher concentration of Cu atoms results in a finer foam structure.