The structure of active mirror Nd∶glass laser amplifier is presented, which is pumped by Xe-lamps. The gain characteristics and energy extraction of the active mirror Nd∶glass laser amplifier are experimentally studied. The size of Nd∶glass is 380 mm×160 mm×30 mm, and the doping concentration of Nd:glass is 2.2%(mass fraction). Experimental results show that when the charging voltage is 23 kV, the small signal gain coefficient of the system is 0.056 cm-1, and the energy storage efficiency is 2.0%. The spot size of the output laser is 126 mm×126 mm and the pulse width is 5 ns when the charging voltage is 22 kV. The laser amplifier obtains the maximum output energy of 349 J when the injected energy is 6.67 J. The peak to valley (PV) value of the static wavefront of the system is 8.38λ.