Ti TES-based superconducting single-photon detectors with different dimensions between 5 μm×5 μm and 20 μm×20 μm were developed. The measured system detection efficiency (η_sys) is 72% at 1550 nm, and energy resolution (ΔE) is 0.26 eV by integrating an optical cavity during the TES fabrication. Based on the two-fluid model, we extract the key parameters (i.e., temperature sensitivity, current sensitivity, heat capacity, et. al) of Ti TES-based superconducting single-photon detectors with different dimensions, and calculate the effective response time and ΔE, which are consistent with the measured ones. The obtained results show that it's possible to realize high η_sys and ΔE by optimizing TES dimension and critical temperature, paving the way for high performance single-photon detectors at telecommunication band.