The pin shaft connection is a commonly used connection component in engineering, the real-time monitoring of its health state under load is vital to the overall stability of the structure. In this paper, a real-time monitoring method for the force state of the pin-shaft connection based on piezoelectric theory is studied by theory and experiment. To identify the force state of pin-shaft connection, the energy of received signal is analyzed based on the wavelet packet theory. The results show that the energy of the received signal is related to the force state of the pin-shaft connection. With the increase of the normal pressure on the contact surface, the energy of the received signal increases, but when the normal pressure increases to a certain value, the energy of the received signal reaches saturation. Therefore, the monitoring method for pin-shaft connection based on piezoelectric theory proposed in this paper has good feasibility and application significance in a certain load range.