Abstract: In the paper, a heave locomotion robotic fish TPF (Three DOFs posture-controllable fish robot) is proposed, which is composed of a multi-linked oscillating tail and a barycenter-adjustor which can change the robot-fish's center of gravity by moving an inside weight. The pitching angle and submergence of the robotic fish are analyzed. In order to make such a biomimetic robot realize heave locomotion and suspend in water, a control paradigm is proposed. In this paradigm, multi-link propulsive system and pitching angle are controlled separately and work together. The propulsive system keeps the robotic fish at a uniform speed based on swimming gaits and oscillating frequency. And a controller with deformation compensation is presented to adjust the turning angle of the barycenter-adjustor's servo motor on the basis of the depth feedback. Experimental results show that the proposed control method is valid, and its performance is much better than that of a general controller in depth maintaining of robotic fish TPF.