As human exploration of nature becomes increasingly in-depth, the demand for new types of underwater vehicles is growing day by day. Biomimetic robots are receiving more and more attention due to their unique propulsion methods and high efficiency. However, traditional biomimetic fish models only imitate streamlined shells, with little consideration given to the impact of the structure of biomimetic objects on biomimetic performance. This paper proposes a biomimetic robot based on a central pattern generator (CPG) that mimics the behavior of the thresher shark. Using the basic movement pattern of fish as a foundation, the fish body is abstracted into a jointed linkage structure, and a biomimetic fish model with three joints and four linkages was established and subjected to simulation calculations. The movement performance was estimated based on gait patterns, and feasibility was subsequently verified through experiments.This biomimetic fish aims to achieve maximum simulation of the thresher shark with simple mechanical structure and economical control costs. Thanks to its well-designed biomimetic structure, the introduction of a central pattern generator, and the application of flexible silicone material in the fish body, this robot possesses characteristics such as small size, simple control, strong terrain adaptability, and high energy utilization efficiency. Compared to traditional underwater propellers, it exhibits lower noise and stronger environmental adaptability. It has broad potential applications in industries such as scientific research, agriculture, and fields like field surveys, underwater rescue, and water patrol.