Flax fiber was used to reinforce Polypropylene (PP) owing to its lower impact on environment and suitable mechanical behaviors. To overcome the difficulty of penetrating fibers due to the high viscosity of thermo-plastic resin, PP filaments wrapping around the linen yam produced commingled yams, which were woven into fabrics as preforms to make laminates by optimum hot-pressing technology. The effects of fiber volume fraction, fabric density and structure on tensile properties of composites were researched through analyzing the tensile test results and the scanning electronic microscope (SEM) micrographs of fracture surface. Concinsious are drawn that the properties of laminates with fiber volume fraction of 0.50 are better than those with the other two fractions. For plain structure, the tensile properties in warp direction decrease according to the increase of weft density while in weft direction increase. For different fabric structures, properties of laminates with structures of plain 3, twill 2/2 and twill 3/1 increase gradually. And properties in weft direction are prior to those in warp direction for each laminate.