The WS2 is used as a saturable absorber in 2 μm band. A low-threshold passively Q-switched Tm, Ho∶LuLiF4 laser with a typical X-type four-cavity structure is demonstrated. The experimental results show that the Q-switched operation starts at the absorbed pump power of 260 mW and becomes stable when it is over 650 mW. When the absorbed pump power is 2000 mW, the output power is 88 mW, corresponding to the typical pulse duration of 4 μs, the repetition frequency of 16.89 kHz, and the maximum single pulse energy of 5.21 μJ. The results show that the WS2 material can be used as a saturable absorber for passively Q-switched lasers in 2 μm band.