Polymeric nano-composites are prepared by melt intercalation in this study. Nano-clay is mixed with either a polymer or a polymer blend by twin-screw extrusion. The clay-spacing in the composites is measured by X-ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEM). Melt viscosity and mechanical properties of the composites and the blends are also measured. It Is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano-clay can greatly increase the viscosity of the polymer when there is a strong inter-action between the polymer and the nano-clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5-10 wt.% nano-clay largely increases the elastic modulus of the composites and blends, while significantly decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano-clay. The effect of nano-clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.