||Permeability, P of a polymer to gas can be written as P=S∙D where S is the solubility and D is the diffusivity of gas. Thus, the low diffusivity and solubility of the gas improves the gas barrier properties of the polymer film. In this study, gas barrier properties of polymer/graphene oxide (GO) composite film were improved by controlling diffusivity and solubility through the lateral size and surface modification of GO. The alkylated graphene oxide (AGO), which have hydrophobic property was synthesized by SN2 reaction between graphene oxide (GO) and octylamine to decrease water solubility of GO. The diffusivity was controlled by using GO of various lateral size (3, 25, 45 μm). Gas barrier properties was confirmed by measured the water vapor transmission rate and oxygen transmission rate of PVA/GO-3, 25, 45 and PVDC/AGO-3, 25, 45.