The invention discloses a low-frequency mechanical antenna based on electromechanical coupling and a signal processing method, and mainly solves the problems of poor stability and low modulation efficiency of a traditional mechanical antenna system in the prior art. According to the technical scheme, the method comprises the following steps: the spherical permanent magnet is fixed by the cylindrical fixing sleeve sleeved with the motor spindle in the same diameter through the high-speed bearing, so that the operation stability is ensured; a high-speed servo motor is used for driving a spherical permanent magnet to rotate and radiating same-frequency electromagnetic waves outwards; the spherical permanent magnet is arranged in a magnetic shielding case of a signal loader, amplitude modulation information on a low-frequency magnetic field is loaded by changing the magnetic conductivity of a shielding case, a modulation signal is filtered and amplified by the signal collector, and then synchronization and demodulation are realized in the signal processor. According to the invention, the stability of a mechanical antenna rotation system is improved, a coding and modulation method adapting to a mechanical antenna modulation signal is provided, the signal processing efficiency of the antenna is effectively improved, engineering realization in information transmission application is facilitated, and the method can be used for a low-frequency wireless communication system.