The passively Q-switched mode-locked (QML) operation of a Tm∶Lu3Al5O12 laser is experimentally demonstrated by employing the reflective MoS2 as a saturable absorber mirror. An absorbed pump threshold of 525 mW with a 3% output mirror is achieved using a tunable Ti-doped sapphire laser as the pumping source and a low-threshold cavity design. Further, a stable QML operation state is obtained when the absorbed pump power is 1743 mW. When the maximum pump power is 3.1 W, the Q-switched mode-locked output power is 306 mW, the slope efficiency is 14.3%, the central wavelength is 2023 nm, the repetition rate is 106.4 MHz, and the maximum single pulse energy is 2.88 nJ. Furthermore, the modulation depth is observed to be close to 100%. The results show that the reflective MoS2 saturable absorber has a potential application in 2 μm laser mode-locked.