passing signal from an amplifier is doped to the noise named amplified spontaneous emission (ASE). To find effective reducing method of this noise needs that we examine effect of the amplifier different parameters respect to it. In this letter we have done a complete analysis of characteristic ASE versus seed energy, gain medium length and small signal gain via stimulating of ASE in a regenerative amplifier. The results will be suit to select effective reducing method of ASE in a regenerative amplifier