A high energy pulsed laser diode (LD) pumped Tm: YAG laser suitable for medical applications is reported. The oscillation operation and output characteristic of the Tm: YAG laser are studied by theoretical simulation and experiment. The results show that the pulsed Tm: YAG laser generates intense relaxation oscillation under pulse pumping state, and can output subpulses with high peak power. When pumped at an appropriate repetition rate, the superposition effect of reversed particles in multi-pulse pumping can significantly increase the single pulse energy. When operating with low-frequency pulses, the laser has a high threshold, which is not conducive to the output. In the experiment, the maximum single pulse energy is 476 mJ at a frequency of 120 Hz and a pulse width of 600 μs, corresponding to an optical conversion efficiency of 26.4%. At an average pump power of 300 W, an average power output of 68.2 W is obtained, with an optical efficiency of 22.7%. The experiment of high energy pulsed laser output at 2 μm above provides reference for laser medical applications.