Abstract: Underwater manipulator plays a key role in underwater operations such as benthic organism sampling and archaeological salvage, but the existing underwater manipulator has some problems such as poor coupling safety, weak adaptability and unstable grasping, which make the operation effect not ideal. Aiming at the above problems, the design and research of a new underwater soft hand are carried out in this paper. Firstly, a bionic soft actuator with compound cavity and sealed tube structure is proposed. Based on the actuator, a three-finger enveloping underwater soft hand is designed. The elasticity of the silica gel material and the compressibility of the fluid can ensure the non-destructive grasping of the target. The sealed tube structure can improve the adaptability to high pressure in deep water. The composite structure of retaining cavity and bending cavity, as well as the bionic structure of fingerprint and fingernail, can improve the coupling adaptability of the soft hand. The soft hand is optimized and fabricated by using the finite element analysis method based on Yeoh model and the processing technologies of injection molding and 3D printing. A hydraulic drive system with high precision is designed to improve the coupling stability of the soft hand. Finally, the experimental tests on the proposed soft hand are performed for the important factors affecting the operating performance of the underwater manipulator by simulating the corresponding experimental scenes. The results show that the longitudinal grasping force of the soft hand can reach 26 N and the driving depth can reach 3000 m, which is higher than the existing underwater soft hands. The results of underwater target grasping test and comparison with the traditional rigid hand show that the soft hand has stable grasping performance, better adaptability and safety, and is suitable for non-destructive grasping of underwater objects.