To study anti-slip characteristics of main cable and saddle of three-tower suspension bridges,a simplified calculation method for calculating anti-slip factor was proposed. Analytical formulas for calculating anti-slip factor were deduced and finite element models were established to verify formulas. The effects of some important design parameters on the anti-slip factor were studied. Analysis shows that the analytical method has a high accuracy,which can be used in preliminary design of three-tower suspension bridges. With the ratio of tower and cable stiffness increasing,the anti-slip factor decreases; when the ratio of tower and cable stiffness is less than 3,changing the ratio of tower and cable stiffness has a great influence on the anti-slip factor. When the ratio of tower and cable stiffness is more than 3,the anti-slip factor is not sensitive to the ratio of tower and cable stiffness. Effect of sag-to-span ratio to the anti-slip factor depends on the tower stiffness. With the increment of span length and the ratio of dead load and live load,the anti-slip factor increases.