Abstract: Tackified fabric is the material which is used in liquid composite molding, and it can improve the shape precision and dimension precision of the composite component. The property of the fabric is changed due to the tackifier. Based on the picture frame experiment, a theoretical model was built. The effects of the bending rigidity and friction coefficient of tackified yarn on the shear behavior were analysed in the article, and the axial force of yarn during the shear process was considered in the model. In addition the variation of width of tackified yarn during the shear loading was observed by the microscope, and the influence of tackifier and fabric architecture was considered. An shear model was derived from the equilibrium equation. The results show that the model can predict the shear performance of the tackified plain fabric well.