High-pulse-energy semiconductor saturable absorber mirror mode-locked 2.0 μm thulium-doped ultrafast all-fiber laser is reported. Stable mode-locked pulse train occurred at 1.8 W incident pump power and the pulse repetition rate is 14.3 MHz in a ring cavity configuration. Increasing the incident pump power to 3.8 W, the maximum output power is 59 mW, corresponding to the maximum single pulse energy of 4.1 nJ. The pulse width is measured to be 2.2 ps, the center wavelength and the spectral bandwidth are 2015 nm and 2.9 nm respectively.