When composite materials occur crack, their fibrous locations will produce bridging fibers. A symmetrical dynamic crack model of bridging fibers in unidirectional composite materials are not probed as deeply by virtue of the complexity, cockamamie and difficulty in mathematical operations. In the light of the theory of complex variable functions, the problems discussed can be facilely translated into Remann-Hilbert problems. Analytical solutions of the displacements, stresses and stress intensity factors under the action of variable loads Pt⁶/x⁶, Px⁶/t⁵ are attained, respectively. After those analytical solutions were used by superposition theorem, the solutions of arbitrary complex problems were acquired.