Based on the principle of double-pass amplification, establishes a double-pass pulse amplifier experimental model. From pulse laser double-pass amplification rate equations, establishes a double-pass pulse amplification theoretical model, studies the transmission characteristics of the pulse in the double-pass amplification system, and obtains the relations between ASE（amplified spontaneous emission）and pump energy, the relations between ASE and the repeat frequency of the signal light, as well as the relations between the gain and the output signal power. Finally, the quality factor Q of the system is derived through calculating.