The thermal debinding behavior of stainless steel foam precursor in vacuum was studied and compared with that in hydrogen. The formation cause of pore channel was analyzed. The experiment results show that the binder removal rate in vacuum is higher than that in hydrogen. In vacuum, the organic compounds can be removed effectively without change of pore size and the pore morphology for the sample. After pre-sintering, some sintering necks form and the sample has certain intensity. The initial surface pore forms with the temperature increasing at first, and then the internal melting binder is aspirated to form initial pore because of the capillary force and the metal powders re-arrange with the migration of binder at the same time.