Abstract: In this paper, we present the experimental measurements of gain and absorption in an e-beam pumped KrF laser amplifier with the self-detection method, which gives useful information for the design of one hundred joules level KrF amplifier and MOPA system. Under the situation of pump rate of 0.67MW/cm²,gas mixture of 89.6%Ar:10%Kr:0.4%F₂ and total pressure of 0.25MPa,measurements result gives a small-signal gain coefficient of 6.6 percent/cm,a nonsaturable absorption coefficient of 0.93 percent/cm and a saturation intensity of 2.5MW/cm²