The invention provides a tail fin propelled deep-sea soft robotic fish. The tail fin propelled deep-sea soft robotic fish comprises a bionic fish head and a trunk / tail fin, the bionic fish head is connected with the trunk / tail fin, the bionic fish head comprises a cabin body and side fins, the cabin body is arranged in the bionic fish head and is arranged in the middle, and the cabin body comprises an energy module and a control module; the side fins are symmetrically arranged on the two sides of the bionic fish head, the trunk / tail fin comprises a propelling module, the propelling module is composed of more than two dielectric elastomer flexible joints which are connected in series, and each dielectric elastomer flexible joint comprises a supporting framework, a dielectric elastomer film, a flexible electrode and a wire. The bionic fish head and the trunk / tail fin are connected through silica gel in an integrated pouring mode, so that deep-sea pressure self-adaption of the soft robotic fish is achieved. The deep-sea soft robotic fish propelled by the tail fin has the characteristics of high efficiency, flexibility and high concealment, does not need a hard shell and a pressure compensation device, can realize low-cost deep-sea detection, and has a wide application prospect.