In this work, poly(L-lactide)/multi-walled carbon nanotubes (PLLA/MWCNTs) nanocomposites with tunable matrix crystallization rate and mechanical strength have been prepared by modifying MWCNTs with different chain length of poly(D-lactide) (PDLA). The PDLA grafted MWCNTs (MWCNTs-g-PDLA) nanohybrids with different molecular weights of PDLA chains were successfully synthesized by altering the reaction time in the ring-opening polymerization of D-lactide monomers on the MWCNTs surface. During subsequent melt-mixing of PLLA with the as-prepared MWCNTs-g-PDLA, the grafted PDLA chains and PLLA matrix chains could co-crystallize into stereocomplex (SC) crystallites (confirmed by TEM, WAXD, and DSC) at the nanocomposites interface. The results reveal that with the increment of grafted PDLA chain length, the dispersion of MWCNTs in the PLLA matrix as well as the tensile strength of PLLA/MWCNTs nanocomposites gets improved obviously, which mainly attributes to the strong interfacial adhesion imparted by the interface-localized SC structure. Moreover, the addition of MWCNTs-g-PDLA nanohybrids leads to an evidently enhanced matrix crystallization rate and the enhancement of the crystallization rate increases apparently with the length of the grafted PDLA chains, confirming the strong heterogeneous nucleating effect of the interface-localized SC crystallites on PLLA matrix crystallization. This work demonstrates the important role of grafted PDLA chain length in tailoring the interfacial adhesion and matrix crystallization rate of PLLA-based nanocomposite