The characteristics of a flash-lamp pumped electro-optic(EO) Q-switched Cr,Tm,Ho∶YAG laser in room temperature is studied.By choosing a Mg-doped LN crystal with high damage threshold as the Q-switch and combining a quarter-wave plate and a flat mirror to minimize the depolarization loss,we realized the EO Q-switched output of the Cr,Tm,Ho∶YAG laser and obtained high energy output.With EO Q-switched repetition rate of 1 Hz,pump energy of 200 J and temperature of 22 ℃,a laser with a output pulse energy of 443 mJ at 2.1 μm,pulse duration of 90 ns was obtained.The mechanism and effect of a quarter-wave plate to compensate depolarization loss were analyzed.The insertion losses of polarizer and LN crystal were measured and analyzed.The phenomenon that the output relies heavily on the repetition rate was also analyzed.