A periodic cubic spline and corresponding calculate method are put forward for describing the tow path of 2D triaxial braided composites. Based on this spline, a method for solving the main material direction of tow element is obtained. The parametric curve of cross-section with asymmetrical lens-shape is created. And twist deformation of cross-section along the tow path is considered. Based on domain superposition method and cutting method, a finer and parameterized unit cell mesh model of 2D triaxial brai...