In order to realize the cross-metal transmission of electrical energy on aircraft surface, based on the vibration mode of metal structure and piezoelectric material, the model of piezoelectric metal composite structure in longitudinal standing wave mode was built and simulated, and the frequency spectrum experiment of composite structure with different thickly was carried out to analyze its resonant frequency variation and phase characteristics. Finally, according to the characteristics, a broadband resonant frequency adaptive tracking circuit is designed, which can act on the metal wall of 5~10mm thickness. Its bandwidth is up to 200kHz, tracking error is less than 1%, and output power is up to 1 W.