In order to improve measurement accuracy of cable tension, define accurately the relation between cable tension and natural vibration frequencies and widen the scope of application of vibration method, by the way of combining the finite difference method with transfer matrix method, the frequency equation is derived from the governing equation with variable coefficients for the free vibration of cable. Transfer matrix method of multibody system is used to compute natural vibration frequencies of cable based on the discrete model. The relation between cable tension and natural vibration frequencies is described by solving characteristic equation. Comparing with the past references, the proposed method has high computational efficiency because of low order of system matrix and can effectively satisfy the requirements for measurement accuracy of cable tension.