Polymer chains were usually grafted on filler to strengthen mechanical property. In this work, dynamic Monte Carlo simulations of cubic lattice model were preformed to investigate the microscopic process of crystallization behaviors of polymers grafted on two-dimensional filler. Some experimental results were reproduced and the microscopic mechanism was studied in detail. Grafted polymers have shorter nucleation induction period and lower ultimate crystallinity. Higher grafting density results in shorter nucleation induction period and higher ultimate crystallinity. The system with low grafting density shows the intramolecular chain-folding nucleation and the system with high grafting density exhibits the intermolecular fringed-micelle nucleation. The orientation of the crystalline bonds is perpendicular to normal direction of the filler for low grafting density, while it is parallel to the normal direction for high grafting density. Those findings are helpful to understand the microscopic mechanism of crystallization behaviors of polymer nanocomposites and also the corresponding reinforcement mechanism. (C) 2016 Elsevier Ltd. All rights reserved.