PLA is considered as the most promising bio-based polymer material for petroleum-based polymers substitution. However, PLA has some shortcomings such as poor gas barrier properties, low thermal stability and crystallization rate. The present paper investigates the effect of starch nanocrystals grafted lactic acid (SNCs-g-LA) on crystallization kinetics and crystalline structure of PLA. First, SNCs were prepared by acid hydrolysis, then lactic acid monomers were grafted on their surface, and finally PLA/SNCs-g-LA nanocomposite films were elaborated using solvent casting method. Crystallization kinetics and crystalline structure were studied using Differential Scanning Calorimetry (DSC), Wide Angle X-ray Scattering (WAXS) and Small Angle X-ray Scattering (SAXS).The results revealed that SNCs-g-LA nanoparticles affect significantly kinetics of crystallization, thermal behavior, aplha-alpha solid state phase transition,and favor the PLA aplha phase.