A new diagnosis equipment is designed to examine the strength of large scale bridge. It is composed of three accelerometers, radio modem, and related electronics parts. Two accelerometers with high accuracy are used for measuring the change of inclination angle of the structure base and two horizontal components of structure vibration. The third accelerometer measures a vertical component of vibration. The equipment is installed in the sidewalk of some Moscow bridges as an application. Several factors such as traffic load, wind, water wave, and etc. cause the vibration of bridge. By means of appropriate processing, the spectral characteristics of the bridge itself are determined. Several month’s test shows that the spectral characteristics remains constant if the bridge state keeps constant, and is changed by the change of the bridge state (for example, before and after repair). If the measured inclination angle of the base is increased to a particular orientation, or the spectrum of bridge is changed, it is assumed that the sagging of the structure base or deformation of its structural members might happen. Periodic or continuous monitoring of the structure state under in-service condition with the help of this diagnosis equipment makes it possible to reveal the beginning of destructive changes in structural members and to prevent the occurrence of an emergency. The study result could be applied to other large structures such as towers and buildings.