In this study, the effect of molecular weight and crystallizability of PLA matrix on the PLA/CNC nanocomposite morphology was systematically investigated using rheological experiments. PLA/CNC nanocomposites containing 1, 3, 5, 7, and 10 wt% of CNC were prepared using solution casting method. The comparison of the effect of PLA molecular weight indicated that CNC could form a percolation network at lower contents when low molecular weight PLA was used as the matrix. This finding attributed to the easier interpenetration of shorter PLA chains and CNC nanoparticles in the solvent. On the other hand, it was observed that the use of PLA with higher crystallizability caused further reduction of the onset of CNC percolation network concentrations. This was because during the solvent evaporation step, which was at around 85oC, the isothermal cold crystallization of PLA around the dispersed CNCs could become more favorable and thereby the heterogeneous crystal nucleation could prevent the driving force of the CNCs towards aggregation