A single-longitudinal-mode Tm, Ho∶YAG laser is realized by using a diode-pumped L-shaped twisted mode cavity. There mainly exist two oscillator wavebands at around 2090 nm in the output spectrum of Tm, Ho∶YAG laser under free running. The maximum output power is 483 mW under pump power of 6.12 W. The single-longitudinal-mode laser possesses a maximum output power of 202 mW at 2090.9 nm under the pump power of 5.9 W, and the corresponding slope efficiency is 6.95%. When the pump power increases to over 5.9 W, the Tm, Ho∶YAG laser runs with multi modes. The output beam radii of single-longitudinal-mode Tm, Ho∶YAG laser are measured with knife-edge method at several positions after the beams pass through a lens. The beam quality factor is about 1.17.