The purpose and significance of bridge health monitoring is described in this paper. Principle of empirical mode decomposition (EMD) and concept of shape factor are introduced. In order to study bridge health monitoring, Firstly, a finite element model for simply supported steel beam is set up on the basis of the Infinite Element Theory and the software ANSYS in response to laboratory experiment. The natural frequency index value and the rate of change can be calculated according to the time-displacement relation curve simulated through finite element method in the way of combining HHT and the frequently used Dimensionless parameters (shape factor) in traditional time-to-amplitude conversion analysis and adding instantaneous excitation to the mid-span, thus the location and the degree of damage can be efficiently identified. Finally, the improvements of this method are discussed.