To solve the problem of reasonable completion state and reasonable construction state determination in cable-stayed bridge design and monitoring calculation, a cable force optimization method based on MOPSO algorithm is proposed. This method adapts to multi-objective and multi-constraint cable force optimization by adding external reserve set and optimizing update strategy based on PSO algorithm. Compared with the single objective optimization method which has the limitation of single solution, MOPSO algorithm considers more comprehensive factors. The Pareto optimal solution set obtained by MOPSO algorithm can be further screened by decision makers based on experience. Python programming language and finite element software are used to compile the optimization program based on this method. The sum of the bending strain energy of the main tower and the main beam is selected, and the sum of squares of longitudinal displacement under dead load is taken as the objective function after the completion of the bridge. The constraints are that the structure is in a safe state during the construction process and after the completion of the bridge and the overall distribution of cable forces is uniform. The optimization results of engineering examples show that the proposed method can quickly find the Pareto optimal solution set and select the optimal solution. The stress of the structure is in the safe range, the main tower is reasonable in alignment, and the overall distribution of cable forces is uniform. The method can be applied to determine the cable force in completion and construction of cable-stayed bridge and the suspender force of girder and arch combination bridge.