Abstract: Different biaxial weft knitted fabrics were produced with glass fiber roving and polypropylene filaments and their lamina composites were fabricated by hot pressing process.The tensile properties and elongation anisotropy of the composites were experimentally investigated.By changing the linear densities of the inserted weft yarns,the influence of the fiber volume fraction on the initial modulus and breaking strength of the composites was analyzed.The breaking forms of the lamina specimens were also studied.The results have shown that there exists a big difference of the tensile properties of the composites tested along or off the inserted yarn directions,and that the initial modulus and breaking strength are proportional with the fiber volume fractions.This means that the insertion of the yarns enhances the mechanical properties of knitted structural composites.