Abstract: In this paper,the low density porous perduterated polystyrene foams with open-network structure,density of 0.02~0.2 g/cm~3,corresponding cell sizes of 10~0.2 μm,and the deuterated ratio above 98% have been fabricated by the thermally-induced phase separation(TIPS) technique and the freeze-drying technique.The experiments show that the morphologies of these foams are determined by the thermodynamics and kinetics of phase separation.