Abstract: The image-source method based Planar Element Method (PEM) and the calculation methods of target strength and its time domain echo are described. By establishing a 3D meshing model of dock landing ship and taking surface reflection and the effect of stern partial flooding into consideration, the target strength of dock landing ship in the horizontal direction, the variation of the echo strength of dock landing ship from far field to near field and the variation of the echo strength of dock landing ship passing over a mine in the shallow water area are calculated and analyzed. Through the acoustic scattering experiment of moving warship model on lake, the time domain echo characteristics of the warship model are obtained and compared with the results of calculation. Research results show that the image-source method based PEM can accurately predict the target strength, the echo strength and echo structure of the dock landing ship, which could provide a reference for improving the stealth characteristics of dock landing ships and avoiding the attack of underwater weapons such as torpedo and mine.