Reduction of intensity or rigidity and losses of quality of the bridge structures can induce the changes of modal parameters of the structure. It is possible to analyze and detect the damage of bridge based on comparing the changes of modal parameters of the structure before and after damaging. Natural frequency, displacement mode and modal curvature are the important parameters in dynamic Analysis. In this paper, their adaptive capacities to bridge damage assessment are discussed. And the damage factor is used to determine the damage location. Model experiments show that the damage factor not only reflects the position of bridge damage, and the damage factor of some vibration mode also indicates the length of damage element. At the equilibrium position of the vibration mode, it is difficult to determine structural damage using the damage factor.