[Objective] The self-excited synchronous motor (SESM) has a simple structure and low cost, utilizing both fundamental current and high-frequency sinusoidal current for excitation. However, the high-frequency current introduces higher-order harmonics, causing interaction between the stator and rotor magnetic fields. This generates radial electromagnetic forces, leading to motor vibration and deformation, and ultimately producing uncomfortable high-frequency electromagnetic noise. [Methods] To address the electromagnetic noise issue caused by high-frequency sinusoidal current excitation, a high-frequency square wave injection excitation strategy was proposed. The strategy utilized the low carrier ratio characteristic of square waves to elevate the injection frequency beyond the human auditory sensitive range (1~5 kHz), effectively reducing noise impact. Firstly, the noise characteristics of high-frequency sinusoidal current were analyzed through power spectral density. Next, the square wave strategy was proposed and its response current spectrum was examined. Finally, the strategy was verified based on magnetomotive force theory and tested on a self-excited motor platform. [Results] The experimental results showed that, compared with the traditional excitation strategy, the proposed high-frequency square wave excitation strategy could reduce the power spectral density in the human auditory sensitive range by 51.86 dB/Hz while ensuring the same excitation effect, significantly mitigating the noise impact. [Conclusion] The proposed high-frequency square wave excitation strategy effectively reduces electromagnetic noise in the human auditory sensitive range, addressing the issue of excessive noise in traditional excitation strategies and providing a reliable low-noise control solution for SESM.