Abstract: Thermoset resin based prepregs exhibit very high tensile modulus and relatively low bending stiffness, and the accurate characterization of such special properties of prepregs is critical to predict and avoid the wrinkle defect during forming process, and improve the accuracy of finite element simulation of composite forming process. In the present paper, a finite element model that accurately tracks the fiber directions was built considering the nonlinear in-plane shear behavior of unidirectional prepregs, and the high tensile stiffness and significantly lower bending stiffness of the prepreg were decoupled using superimposed membrane-shell elements. Besides, the tensile stiffness, no-linear shear stiffness, and bending stiffness of the domestic prepreg system AC531/CCF800H were characterized experimentally. Finally, the 30° off-axis tensile test and axial compression test were used to prove the validity of the proposed model, respectively.