设计了大型ＫｒＦ准分子激光器放大自发辐射的三维和准三维计算程序，比较了两种方法的差别。通过对不同纵横比、增益吸收比及注入光强条件下，放大自发辐射（ＡＳＥ）及提取效率的计算，明确了影响提取效率的主要因素．当注入强度为０．１饱和光强时，其噪信比（ＡＳＥ强度与相干光输出强度比）约为５％。 A three-dimensional and quasi-three-dimensional calculation program of large-scale KrF excimer laser to amplify spontaneous emission was designed and the difference between the two methods was compared. Through the calculation of ASE and extraction efficiency under different aspect ratio, gain absorption ratio and implantation intensity, the main factors that affect the extraction efficiency were clarified. The noise-to-noise ratio (ASE intensity to coherent light output intensity ratio) is about 5% when the injection intensity is 0.1 saturation light intensity.