Polypropylene/polypropylene-graphene (PP/PP-GR) alternating multilayer composites with regular alternating layer structure were prepared by multi-layer coextrusion technology. The relationship between the structure and properties of PP/PP-GR alternating multilayer composites was studied by optical microscope, scanning electron microscope, gas permeation experiment and mechanical property test. The results show that the "biaxial stretching like" effect of laminating-multiplying elements on the composite materials makes the melt wider and thinner, and promotes the dispersion, exfoliation and orientation of GR in PP, which makes the PP / PP-GR alternating multilayer composites show both high gas barrier properties(oxygen permeability coefficient of 1.01×10-15 cm3·cm/( cm2·s·Pa)) and a high elongation at break (1080.1%) even with the low content of GR (volume fraction of 0.082%).