Abstract: Expandable polypropylene (PP)-based resin was prepared for microfoam sheets by using homopolypropylene (PP-H) and block-copolymerized polypropylene (PP-B) through a melt-blending method, and effects of PP-H content on mechanical properties of microfoam sheets were investigated. In addition, foaming modifier and nucleating agents (calcium carbonate and talcum powder) were used to modify microfoaming behavior of PP resin, and effects of contents of foaming modifier and nucleating agents on foaming behavior of PP were also studied. The results indicated that the tensile strength of microfoam sheets decreased but their flexural strength increased with an increase of PP-H content. The foaming modifier improved the melt strength of PP. The density of microfoam sheets decreased but their cell density increased with increasing contents of nucleating agents. As an appropriate amount, 0.5 phr of nucleating agent was recommended for the microfoam sheets. The modified PP exhibited an increase in shear viscosity and extrusion expansion ratio, and however, its molecular weight distribution almost did not changed. These microfoam sheets were found to have a cell diameter less than 50 μm and a cell density up to 106 cell/cm3.