Abstract: To investigate the sound scattering characteristics of three paralleling flexible cylindrical shells with plane incident wave,a mathematical model is established with Fourier series expansion method which involves the flexible vibration,sound radiation and rigid scattering of each shell and their coupling through the sound field.With the model,the difference between the flexible radiation term and rigid scattering term of the sound field of three combined cylindrical shells is calculated and analyzed,ais well as the scattering strength of the shells.The results demonstrate that the flexible radiation term is supposed to be ignored for ka₂>40(f>3000 Hz),and for the instance of ka₂>30(f>2400 Hz),the scattering strength error without the flexible radiation term is less than 3 dB.The scattering strength of three shells is approximately equal to the scattering strength of single shell while the incident angle is 0°or vicinity angle,whereas the scattering strength of multi-shells is higher than that of single shell for the distinct incident angle.The mathematical model in this paper could be easily extended to solve the problems of scattering and reflection of random number of resistant cylindrical shells.