The experimental research progress of 2.0 μm-band Tm-doped continuous wave (CW) single-frequency fiber laser is introduced. With a focus on the key technologies in realizing the single-frequency fiber lasers, the present research status and development directions of the Tm-doped single-frequency lasers with different cavities are summarized. Based on master-oscillator power amplifier (MOPA) of laser seeds, the power amplification of single-frequency lasers is realized and the research progress of high-power Tm-doped single-frequency fiber MOPA lasers at home and abroad is summarized. In addition, some research works in our research group related to the fabrication of highly Tm-doped germanate glass fibers, the construction of 2.0 μm-band single frequency laser oscillators, and the power amplification of single-frequency lasers are presented.