In view of the lack of theoretical research of multi-pass pulse amplification system, established multi-pass pulsed amplification theoretical model based on the basic principle of multi-pass amplification and the rate equation of pulse laser multi-pass amplification, and studied the transmission characteristics of pulse in multi-pass amplifying system. Through the simulation research of the theoretical model, obtained the relation of output power and pump power and the relation of output single pulse energy and pulse repetition frequency.