Abstract: Echo characteristics of a small type submersible vehicle are investigated by using planar element method which is commonly used for forecasting echo strength of targets. The effects of incident plane wave frequency and incident azimuth angle on the acoustic scattering characteristics are calculated and analyzed. According to the scattering characteristics obtained by plate element method, the acoustic imaging results are simulated by the frequency-domain indirect method. The field experiments show that the experimental and the numerical results are in good agreement. The results show that the mast structure has a significant influence on the scattering results.