Nano-sized as-synthesized MCM-41 particle, whose pore channels and outer surface full of organic CTAB template, was used as compatibilizers for immiscible polypropylene (PP)/polystyrene (PS) blends. In this paper, the solid structure SiO2 was selected to compare with as-synthesized MCM-41 in properties of PP/PS blend. The mechanical results showed that tensile strength of the blend was increased by 32% and the impact strength was increased by 41.1% by addition low content of as-synthesized MCM-41 compared to pure PP/PS. The presence of SiO2 in the blend cannot improve the mechanical properties obviously. SEM indicated that incorporation of as-synthesized MCM-41 into PP/PS blend can act as compatibilizer, which resulted in a decreased particle size of dispersion phase together with morphological evidence of interfacial adhesion. However, with the presence of SiO2, 1%, 3%, in the blend, the interface did not show clear change compared with the PP/PS blend.