Abstract: With poly(4 methyl 1 pentene)(PMP) as the foam skeleton material, durene/naphthalene as the solvent/non solvent system and silicon containing polymer as the doping material, Si doped CH polymer foams are successfully prepared with the density of 5～ 80 mg/cm 3, and the mass percentage of Si in the foams is less than 1%. The paper presents the fabrication procedures of Si doped CH polymer foams, and the parameters which influence the properties of the foam products are discussed in detail. The thermal analytical technique(TG DSC) is used to measure the foam's thermal properties. It is found that the foam's thermal stability varies with it's density.