The nonisothermal crystallization behavior of the MC nylon 6/ZnO nanocomposite prepared by in situ polymerization was studied by means of differential scanning calorimetry (DSC), where a kinetic analysis was made by Jeziomy, Mo and Kissinger methods based on modified Avrami equations. The results showed that the nucleus growth of MC nylon 6 is accelerated because the nano-sized ZnO particles are playing the role of nucleating agents to expedite the crystallizing rate and raise the temperature of MC nylon 6. At the same time, the movement of MC nylon 6 molecule chains is suppressed in crystallization process due to the interaction between nano-sized ZnO particles and MC nylon 6 molecule chains, thus increasing the activation energy of MC nylon 6 crystallization and decreasing the crystal growing rate and crystallinity.