A nonlinear force method model is proposed to study the dynamic behavior of cable trusses. In the paper, travelling wave method is employed to solve the governing equation of motion. After support reaction forces are considered as excitations, cable trusses are extended to infinitude, and D’Alembert solution to the partial differential equation (PDE) is achieved. Substituting the solution into compatibility condition and boundary conditions, the governing equation expressed by dynamic tension is derived, which is named force method dynamic equation (FMDE). Hence the dynamic system of infinite-degree-of-freedom is simplified as a system with only one unknown without any loss of precision. Nonlinear governing equations are developed through considering the effect of quadratic terms of displacements. At last, an example is given to verify the force method model presented in the paper.