A model of finite element analysis was proposed to calculate mechanical properties of single ply of woven fabric composites considering interfacial properties. In this model, microfracture in the fiber bundle was regarded as interfacial fracture. Woven fabric structure was modeled using a pair of parallel beam elements expressing a fiber bundle and an interphase element between the two elements. Stress of the composite was calculated at the fracture of each element under tensile load, and the fracture process was simulated. The first fracture occurred in the interphase along the transverse bundle. Secondly, resin at the surface of the composite was seen to fail as did the longitudinal fiber. The stress of the composite at the interphase fracture was calculated with various properties of the interphase. The calculation showed that the lower modulus and higher strength interphase has high resistance to the microfracture. Another calculation was carried out with different weaving densities to evaluate the effect of the geometrical structure of the fabric on the microfracture. Weaving density was less effective than interfacial strength on the stress at the interphase fracture.