The characteristics of seed light directly affect the characteristics of amplifying pulse. In order to obtain high quality amplifying pulse output,the seed light characteristics of passive mode locked fiber amplifier based on SESAM are optimized and simulated in this paper. The influences of the length of the single mode fiber,the length of the gain fiber,the filter bandwidth and the output coupling ratio of the mode locked fiber laser on the optical properties of the seed and the effect of chirp carried by the seed light on the amplification pulse are analyzed theoretically. The optimal values of various parameters are obtained by integrating the effects of dispersion and nonlinear effects on the seed light,and the two stage amplification simulation is carried out. Finally,a high quality amplification pulse with a pulse width of 12.79 ps,a spectral width of 13 nm and an average power of 6.1 W is achieved.