Abstract: To study the parameter choice during the preliminary design stage of the multi-tower suspension bridge, static mechanics analysis model was set up for multi-tower suspension bridges by using main cable equivalent to a spring with some stiffness. Calculation methods for deformation of multi-span suspension bridges were proposed based on balance of horizontal forces between loaded span and unloaded span. Analytic expressions of main cable deformation were derived and validated, which could be applied in the preliminary design. Effects of major design parameters on the deformation of multi-tower suspension bridges were studied. Research shows that changing sag-to-span ratio has a little influence on the deformation; tower stiffness imposes a significant effect on deformation, and structural deformation decreases with a increment in tower stiffness; with the increment of span length and the ratio of dead load and live load, the structural deformation decreases; increasing the number of main span almost has no effect on deformation of the structure when there are more than three main spans.