Polypropylene (PP)/low-density polyethylene (LDPE) foam composites were prepared by the extrusion and a subsequent post-foaming process in a designed die. Hollow glass beads (HGB) were added to improve the performance of calcium sulfate whisker (CSW)-reinforced PP/LDPE foam composites. The influence of the content of HGB on cell structure and mechanical properties of the as-fabricated PP/LDPE foam composites reinforced by CSW was investigated. It was found that the introduction of HGB could enhance the cell structure of the PP/LDPE foam composites characterized by the reduced mean cell diameter, the increased cell density, and the uniform distribution of cell size. The mechanical properties tests indicated that HGB could significantly improve the compressive properties of the PP/LDPE foam composites in particular.