Tunable Tmfiber lasers within a wavelength range around 2 μm have numerous applications such as communications, lidar etc.. In this paper, a high power, widely-tunable Tmfiber master oscillator power amplifier (MOPA) system is reported. The master oscillator is tunable over 160 nm (1921～2084 nm) by use of a diffraction grating, which is placed in the Littrow configuration to provide wavelength selective feedback. The MOPA laser is tunable over 140 nm (1936～2081 nm) and continuous-wave output power higher than 54 W is obtained over a tuning range of 100 nm from 1962 nm to 2066 nm, limited by the seed laser tuning range. The laser yields 77.4 W output power at 1981 nm, corresponding to a slope efficiency of 34.4%.