PLA/ ECNC blend films were prepared using polylactic acid (PLA) as the matrix and esterified cellulose nanocrystals (ECNC) as the additive. The effects of cellulose nanocrystal (CNC) and esterified cellulose nanocrystal on the light transmittance, surface morphology, thermal stability, hydrophilicity and mechanical strength of PLA films were investigated. The results showed that the compatibility of ECNC with PLA was increased, and the light transmittance, thermal stability and mechanical properties were also enhanced compared with CNC. Esterified cellulose nanocrystals reduced the hydrophilicity of CNC, thereby enhancing the interfacial adhesion with PLA. In addition, the content of CNC in the PLA blend film was increased from less than 1% to 5%. The PLA/ECNC blend film has potential in the field of packaging plastics, and provides a simple and feasible method for the preparation of biodegradable packaging plastics with better performance.