Abstract: This paper presents a theoretical study on the resonators of Chinese bowed-string instruments,Jinghu and Erhu.From the analysis of couple motion of membrane and air in resonator-cylinder,approximate solutions for resonant frequencies and resonant response of the resonator are given.The calculated resonant frequencies are conformable with that of experiments.The acoustic impedance of grate opening at the rear end of the resonator has been calculated from the experimental distribution of sound pressure in the resonator-cylinder to show the effect of grate opening on the characteristics of the resonator.The frequency response of sound radiation is given by ratio of sound pressure to the vibrational velocity of the string at the bridge.