Abstract: Nano-ZnO/MC nylon 6 composites were prepared by the in situ polymerization method. The mechanical properties, morphology, structure and DSC, XRD analysis show that the inorganic particles disperse very well in the matrix and their diameters are smaller than 100nm. The tensile strength, break elongation, bend modulus and impact strength increase by 20%, 33%, 36% and 87% respectively compared with pure MC nylon. Nano-ZnO does not influence the characteristic peak of α-crystalline diffraction, and the crystal modality of nylon 6 is unchanged. The size of the grain is increased and the crystallinity is decreased for nano-ZnO adding. The dynamic XRD analysis shows that nano-ZnO increases the melting temperature of nano-ZnO/MC nylon 6 composites, while the crystalline morphology and relative crystalline degree are reversible among high and low temperatures.