We demonstrated a high-energy single-frequency erbium-doped yttrium aluminum garnet (Er:YAG) laser. With 1470 nm laser diodes (LDs) as pumping sources, single-frequency laser pulses with energy of 28.6 mJ, 21.6 mJ, and 15.0 mJ are obtained at pulse repetition frequency of 200 Hz, 300 Hz, and 500 Hz,