Resonant beam is a kind of widely used resonator. The axial load can be solved by measuring the resonant frequency of the beam, and the measurement purpose is achieved. The current frequency measurement method of resonant beam is not effective for dynamic circumstances and is restricted in many applications. In this paper, we focus on the problem of the frequency measurement of the double ended resonant beam, and propose a method based on Hilbert transform. Numerical method is used to solve the vibration equation of the resonant beam, and a variety of typical test signals are obtained. The simulation results show that the method can precisely obtain the frequency of dynamic signal.