Abstract: According to the structural responses of two span cable-stayed bridge with a single tower under live load, a conception of "the influence degree of cable load effect"is put forward and used to quantitatively analyze real function of cables of cable-stayed bridge with low towers. A parameter, "the characteristic parameter of cable-stayed bridge with low towers"which can comprehensively reflect the structural and mechanical properties of cable-stayed bridge with low towers, is put forward. With the coherency of "the influence degree of cable load effect"and "the characteristic parameter of cable-stayed bridge with low towers" the properties of cable-stayed bridge with low towers are quantitatively described. Valuable conclusions are drawn which are helpful for further understanding the properties of cable-stayed bridge with low towers.