We demonstrated a compact cavity-dumped Q-switched Yb:YAG laser based on a 72-pass pump module. A highly stable nanosecond pulse laser with a duration of 18.38 ns was achieved at a repetition rate of 100 kHz, which is pumped by multimode laser diode stacks at 969 nm. The average output power of more than 150 W is delivered in a good output beam characterized by M2 = 1.53. The result shows that the pulse duration derived from simulation agrees well with the one retrieved from the experimental measurements. To the best of our knowledge, the 43.5% optical-optical efficiency is the highest reported to date from a cavity-dumped Q-switched Yb:YAG TDL (thin-disk laser).