The objective of this research was to prepare polybenzimidazole- polydiallyldimethylammoniumchloride- graphene oxide (PBI-PDDA-GO) composite membranes by layer-by-layer assembly for direct methanol fuel cell. The pure PBI, 5-layered PDDA-GO and 10-layered PDDA-GO composites on PBI were prepared and tested for conductivity, methanol permeability, and direct methanol fuel cell performance. The purposes are to decrease permeability by using GO and to increase ionic conductivity using PDDA to attain enhanced cell performance. The ionic conductivity of the 5-layered membrane exhibited a value of 1.46×10-2 S/cm at 30oC, much higher than those of the pure PBI membrane (1.12×10-2 S/cm) and 10-layered composite membrane (0.84×10-2 S/cm). The 5-layered composite resulted in the highest open-circuit voltage in fuel cell test. The cell voltage drop in the ohmic loss region of the polarization curve was the least among three membranes. Therefore, this 5-layered composite performed the highest peak power density of 230 mW cm-2. On contrary, the 10-layered composite had the lowest conductivity and resulted in higher voltage drop. Despite of its higher open-circuit voltage than the PBI film, the 10-layered composite demonstrated the lowest power density. Keywords: graphene nanocomposite, layer-by-layer assembly, alcohol fuel cells, ionic conductivity.