Based on the deflection theory and equal-substitute beam method, the reasonable rise-span ratio and height-span ratio were suggested.A single-tower suspension bridge was designed according to the proposed rise-span ratio and height-span ratio, and was compared with a three-tower suspension bridge.According to the results, the number of main cables and the tower's construction cost of a single-tower suspension bridge reduced by 14% and 3.5%, respectively, as compared with a three-tower suspension bridge.The ratio of deflection to span, the maximum rotation angle of the main girder and the longitudinal displacement of the tower top in a single-tower suspension bridge are lower than that computed for a three-tower suspension bridge separately under live load.Therefore, a single-tower suspension bridge is more economical and competitive, compared with three-tower suspension bridges.