At present, robotic fish made mainly of rigid materials have good control accuracy and relatively fast swimming speed in water. However, due to the high rigidity of rigid materials, the robotic fish usually cannot adapt well to the narrow passages in water. To solve the above problems, the origami structure was applied to the structural design of robotic fish, and a soft robotic fish that could pass through narrow passages in water and had good swimming performance was designed. This robotic fish was composed of a head, a trunk and a tail. The trunk part adopted the Water Bomb origami structure, and the radial change of the trunk part was achieved by the contraction and expansion of the origami structure. The tail used the bending of the soft origami driver to achieve swing, thereby enabling the forward movement and turning of the robotic fish. The movement of the robotic fish in the water tank was measured through experiments. Its maximum swimming speed was 72.67 mm/s, the fastest turning speed was 10.67 (°)/s, and it could move stably under the condition of a maximum load of 150 g. The results show that the designed robotic fish can not only move flexibly in water, but also utilize the folding characteristics of the trunk part to pass through some narrow passages and obstacles, which provides a new idea for the design and research of soft robotic fish.