Abstract: Poly(ethylene oxide) (PEO)-polypropylene (PP) blends containing organic-montmorillonite (OMMT)/poly(ethylene oxide) (PEO)-polypropylene (PP) composites were prepared using a twin screw extruder followed by the injection molding. The effects of OMMT loading on the morphology and transparent properties of the OMMT/PEO-PP composites were investigated in detail with a combination of TEM and SEM measurements. The crystallization and melt behavior of OMMT/PEO-PP composites were studied by means of DSC and POM. It is found that in all blends the OMMT are preferentially located within the PEO phase and around the interfaces of PEO and PP phases. SEM reveales a large reduction in PEO domain size when OMMT is used. The PP crystal sizes decrease significantly with OMMT content increasing. It is also shown that the incorporation of a small amount of OMMT induces a dramatic transformation from an opaque to a transparent system.