In order to research the underwater echo characteristics of elastic shell, the numerical expressions of surface sound pressure and particle vibration velocity are derived based on finite element and boundary element theories. The echo characteristics of hollow coaxial cylinder-cone assembled elastic shell are calculated with simulation and experiment methods to obtained the azimuth angle and frequency characteristics. It's shown in the results that the more quantity of mesh point, the higher precision of calculation. Meanwhile, the magnitude of mirror reflection wave is largest in the echo wave between 20 and 40 kHz, and increases as the scattering cross-section. The backscatter sound pressure of elastic shell has the obvious frequency characteristic.