Abstract: It is theoretically proved that there not, in some cases, exist solution for the state equation of cable segments of suspension bridges. The problem that the convergent path in the numerical-analytical method should be searched in the iterative calculations for main cables system of suspension bridge in the finished dead state at design base temperature is solved. Aim at the shortcomings of the old numerical-analytical method that there would be no solution obtained sometimes, a search algorithm with the penalty factor is introduced to improve it. The formula for determining the proper value of the penalty factor is derived. An iterative procedure with high precision and speed is established and the convergence requirement can be satisfied. A testing example has proved that the improved method is effective while the unimproved method can’t converge.