This paper aims to disclose how the size of TiO2 Nanotubes affects the performance of Li-ion battery with TiO2 nanotubes as anode material. Firstly, TiO2 nanotubes of two different sizes were synthetized by hydrothermal method, namely, L-TiO2 nanotubes and S-TiO2 nanotubes. Next, the morphology, structure, cycle performance, rate performance, and electrochemical performance of the button batteries respectively assembled with L-TiO2 nanotubes and S-TiO2 nanotubes as anode materials (L-battery and S-battery) were tested with a scanning electron microscope (SEM), a transmission electron microscope (TEM), an X-ray diffractometer (XRD), a battery test system, and an electrochemical workstation. The results show that S-battery has better specific discharge capacity (SDC), cycle stability and rate performance than L-battery. The initial DSC of S-battery was as high as 262.6mAh/g; after 100 cycles, the DSC of that battery was still 250.5mAh/g, down by only 0.046%. Even if the rate increased to 2C, the DSC of the battery was maintained at 151.8mAh/g.