In order to expand the use of water flow, this paper presents a generating device using the vortex-induced vibration to gather energy from the low speed water flow. The device consists four parts: bearing frame, transmission and power generation system, vibration system and the measuring system. A prototype was made according to the design scheme, and finished the experimental test in a circulating water channel. The experiment showed that: the vibration body could get higher amplitude to drive the generator by controlling its stiffness coefficient; the unidirectional rotation transformed from the vortex-induced vibration reciprocating motion fluctuate obviously, which can be transferred into smooth rotation by the energy storage flywheel to drive the generator. The design and study of the swing arm vortex-induced vibration generating device provided a new idea for gathering energy from low-speed water flow, it would also provide a reference for the theoretical study and engineering applications of using vortex-induced vibration for generating.