Numerical simulations in recent years have shown that vortex-induced vibrations (VIV) of cylinders can occur at subcritical Reynolds numbers as low as 20, but relevant experimental evidence for the existence of such phenomenon has not been observed. In this paper, we first built a rotating channel for low-Reynolds-number experiments. Then, VIV at subcritical Reynolds numbers were studied in this rotating channel. The effects of support stiffness and Reynolds number on the VIV were investigated. The lowest Reynolds number for the occurence of VIV of a cylinder is 23, which is close to the numerical simulation results. It confirms that the subcritical VIV indeed exists. In addition, von Kármán vortex shedding was found during VIV and the vortex shedding frequency is the same as that of the cylinder. It indicates that the elastic support makes the flow less stable, which also agrees well with previous numerical results.