Nowadays, preparation of poly(lactide) (PLA) with high content of stereocomplex crystallites (SCs) is receiving more and more attentions. The stereocomplex formation between enantiomeric poly(l-lactide) and poly(d-lactide) can efficiently improve the corresponding mechanical properties and thermal stability. In the current work, using dynamic Monte Carlo simulations, the microscopic mechanism of SC formation in grafted polymers was investigated. The increase in grafting density can lead to the enhancement of SC formation. On one hand, the miscibility between the chains of different types can be improved due to the grafting. On the other hand, the increase in grafting density can result in the higher degree of chain extension and the change in crystal nucleation and growth modes. The changes facilitate the stereocomplex formation. These findings not only provide an effective way to prepare PLAs with high content of SCs, but also reveal the underlying mechanisms controlling the SC formation. (c) 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 89-97