Abstract: To improve the forming performance of low density polymer foams and to meet the requirement of ICF physical experiments, the forming control of low density polymer foams was studied using thermally induced phase-inversion technique combined with in situ moulding or machining. The results indicate that the fine structure and homogeneity of the foam were preserved by quenching the liquid gel to liquid nitrogen under appropriate nitrogen pressure, and after the solvents being released, the resulted PMP foams had higher strength, more uniform microstrucure and finer pore size. By using in situ moulding or machining, precision forming control of low density PMP foams could be achieved.