Abstract: In order to study the static characteristic of the triple-tower-four-span suspension bridge under a dynamic load, the traditional deflection theory of single span suspension bridge was expanded to the theory of multi-tower-multi-span suspension bridge. Based on the expanded theory, the corresponding nonlinear differential equations were established, and then an equivalent beam method were employed to solve the equations. The static characteristics of the multi-tower-multi-span suspension bridge were analyzed by a program developed using MATLAB for the purpose of calculating the internal force and deflection. The nonlinear effect of the main cable force increment due to the concentrated load was considered when the lines calculation was affected. The calculation results showed good consistency in both bending moment and deflection between the deflection theory and finite element method. The maximum deflection deviation was 5.3% and the maximum bending moment was 13.9%. The maximum girder deflection was located in the middle of the two mid-span. The results of deflection and bending moment calculated by the deflection theory were greater than that of the finite element method, thus, a structure designed according to the deflection theory is considered safer. Calculation results also indicated that the deflection theory has broad application future in the triple-tower-four-span suspension bridge and can also be applied in static analysis of the multi-tower-multi-span suspension bridge, especially in the preliminary or conceptual design stage.