In order to determine the cable force of the cable-stayed bridge of the low tower cable-stayed bridge, the optimization model of the cable force of the cable-stayed bridge of the low tower was established on the basis of the influence matrix of the cable force of the cable-stayed bridge, and the solution method of the initial tension optimization was established by using the gradient projection method. Combined with the Yinhu Bridge example, the CBOP program based on the optimization model in this paper is used to optimize the initial tension of the cable-stayed cable, and the calculated results are compared with the original design of the bridge cable force. The results show that for the low-tower cable-stayed bridge, the initial tension of the cable optimized by the gradient projection method will make the bending moment diagram of the whole beam change more smoothly, and the structural force will be more reasonable, and the optimization rate of the maximum negative bending moment will reach 49% and the maximum positive bending moment will reach 14% when the initial tension increases by 6%. On the whole, the optimization effect of this method is good, and it can be applied to the design practice of existing bridges.