The effect of gap ratio on elastic properties of plain weave fabric( PWF) and laminate with triaxial weave fabric(TWF) and PWF composites was numerically investigated by FEA method. Firstly, based on geometry construction and basic parameters of PWF composites, the relationship was determined between both surface density and length of representative unit cell and gap ratio. Secondly, the tension, compression and tear model of PWF composites are established to study the effect of gap ratio on elastic properties of PWF composites. Finally, the effect of the gap ratio on the laminate with PWF and TWF composites was investigated. It is found that the specific stiffness of tension and compression increase with the increasing of gap ratio, and the specific stiffness of tear increases with the increasing of gap ratio. The polarity of polar curve of equivalent stiffness of laminate with PWF and TWF composites decreases with the increasing of gap ratio of PWF composites.