The radiation cross-linked low-density polyethylene (LDPE) foams have been formed by use of supercritical carbon dioxide (scCO,2,) as a blowing agent at a batch scale. The effect of irradiation with different radiation doses on melt temperature and crystallization of LDPE has been characterized by a differential scanning calorimeter (DSC). The morphology of resulting microcellular structures has been investigated by scanning electron microscopy (SEM). The effects of radiation dose, treated temperature and pressure on morphology of the radiation cross-linked LDPE foams are studied in detail. The optimum radiation dose for the foaming of LDPE is found to be 50 kGy. Higher foaming temperature results in larger cell size and lower cell density, while higher saturation pressure leads to smaller cell size and higher cell density. Furthermore, the radiation cross-linked LDPE shows an improved thermal stability and foamability in comparison with the original LDPE.