Based on the motion rules of three-dimensional four-directional braiding yarn carriers and the interior fiber bundle's force analysis

a mesoscopic modeling approach using energy method was established

which divided the modeling process as follows: adjusting the control point after jamming of fiber bundle

changing the position of fiber bundle due to extrusion and interwinding to each other and establishing the fiber bundle trajectory according to the minimum strain energy. By analyzing the geometric dimension of unit cell model

the relationship between unit cell model and braided parameters was provided. The fiber bundle model established by this approach was not interfered but compacted

and the fiber bundle trajectory

composed of a space curve and two tangent lines

was almost a straight line. Compared with the experiment result

the fiber bundle trajectory and cross section of model are consistent with the electron microscope scan images

and braided structure size calculated is in agreement with the measured data. The maximum relative calculation error of pitch length is about 5%

especially when braided angle is 21 degree or so

the relative calculation error is below 2%.