Abstract: A micromechanical finite element method——parameterized double-random distribution model of virtual reality was developed. Integrated with the real microstructure character of fiber reinforced resin matrix composites and discrete characteristics of testing results about mechanical properties for monofilaments, random distribution of fiber arrangement and fiber strength were both simulated in the model. The reliability of parameter random distribution model was studied with moving window method and the size of its representative volume element was determined. The predicted formulas of elastic modulus for unidirectional composites were derived based on energy method. Combined with energy method and progressive failure analysis, elastic modulus and strength properties of unidirectional fiber reinforced resin matrix composite T300/5228 were respectively predicted by the micromechanical finite element method. The numerical results agree well with most experimental data, which shows that the micromechanical finite element method can predict the mechanical properties of composites correctly.