Abstract: In order to study the motion characteristics of the eccentric cylinder in low-speed flow such as ocean current and its energy transformation, experiments on eccentric cylinder flow were carried out. The angle swing and torque varying with time were measured. The motion characteristics, hydrodynamic performance, and the chaotic characteristics of the eccentric cylinder flow dynamic system were analyzed. The average output power and energy conversion efficiency were calculated. The results show that a certain starting flow rate is required for the motion of the eccentric cylinder. The energy transformation efficiency of the eccentric cylinders is linearly proportional to the damping and decreases with the Reynolds Number. The maximum conversion efficiency can reach 37%. The eccentric cylinder flow dynamic system is a weak chaotic system, and its motion law can be approximated using a linear equation. According to Strouhal Number similarity and the fitted equation, the motion and energy conversion efficiency of the prototype eccentric cylinder flow were predicted. The research results provide a theoretical and experimental basis for the equipment design and utilization of ocean current energy.