The utility model relates to a frequency tracking device of a wireless energy transmission system. The frequency tracking device comprises a full-bridge inverter circuit driving circuit, a DDS chip, a single-chip microcomputer, a phase difference detection circuit, a primary winding loop, a voltage sampling circuit, a current sampling circuit and an amplification shaping circuit. The utility model also discloses a frequency tracking method which is applied to the frequency tracking device of the wireless energy transmission system. The frequency tracking method comprises the following steps that: 1, the single-chip microcomputer reflects the results of frequency tracking into frequency data and transmits the frequency data into the DDS chip; 2, control quantity outputted by the phase detection circuit can keep constant in a detuning or resonant state; and 3, the single-chip microcomputer timely updates frequency control words of the DDS chip, and generates new operating frequency to drive an inverter circuit, and at the same time, the phase detection circuit performs circulatory detection and judgment until the system restores resonance. The frequency tracking device of the wireless energy transmission system of the utility model is simple in structure and can assist in effectively solving the problem of frequency detuning in the wireless energy transmission system.