Pipa fretting and pitch measurement are crucial aspects of playing. In this paper, Pipa’s string vibration is simplified to bounded string vibration, and a simplified structural model of Pipa is built. Transverse free vibration is used to establish the vibration equations of Pipa strings, and differential analysis is used to analyze the standing waves. Meanwhile, the vibration of the resonance panel of the Pipa was abstracted into a dynamic model, and the modal analysis was performed using coordinate transformation. In the actual test, the sound signal generated by the vibration was also processed with the help of the Fourier transform, and the pitch of the Pipa was measured by analyzing the time and frequency domains. The vibration of the Pipa panel is complex but regular, with the vibration pitch line at 32.5 hz being a central axis and the vibration pitch line at the frequency of 85 hz being on the upper side, while the vibration corresponding to the frequencies of 32.5 hz and 85 hz can be regarded as a synthesis of the vibration corresponding to the frequency of 175.5 hz. Under the viewpoint of vibration modal analysis, the performance effect of the Pipa has a more refined expression.