Abstract: Pi-Pa is an important plucked string instrument in China. This paper gives a general description of the acoustical properties of pi-pa. The vibrational modes and radiation characteristics of soundboard are analyzed. The vibrational modes show that the bridge acts as a complex lever with distributed parameters in the medium frequency range. The frequency characteristics of Pi-pa sound can be described from the envelope of sound spectra obtained by playing seven notes. The envelope has a peak in each frequency band of 1kHz. The specialities of some fingerings and techniques for playing the Pi-pa are discussed in this paper.