This study experimentally investigated a Yb: YAG pulse laser amplifier with a high amplification gain and a high signal-to-noise ratio (SNR). The highest amplification gain of 172 and highest pulse energy of 131 mJ were obtained with the highest SNR of 24.9 dB from a volume gain of 10 mm × 10 mm × 1 mm. The output beam quality values of M²_x = 1.91 in the slow axis and M²_y =1.58 in the fast axis were also achieved.