The ultra-thin (polyethyleneimine/graphene oxide)n [(PEI/GO)n]multilayer films on poly(lactic acid) (PLA) were constructed via the layer-by-layer assembly. Here, the electrostatic interactions between PEI and GO were used to obtain the nanoscale composite membrane of (PEI/GO)n on the surface of PLA film. With the number of assembling layers increased, the oxygen permeability (PO2) of PLA film decreased substantially. As a 0.06wt% GO solution was used with only four layers, the PO2 decreased from 53.8 to 0.377 × 10-4 cm³/m²/d/Pa, only 0.7% of the original PLA film. At the same time, the coated PLA film also presented a good transparency and better mechanical properties. It is a novel way to use GO on biodegradable packaging materials.