在利用激光导引星的自适应光学系统中，焦距非等晕性是对自适应光学系统性能的主要限制，利用湍流探测配置的孔径滤波函数导出了剩余波前畸变方差．并依此导出了成像系统的有效直径ｄ０，根据昆明和兴隆实测的大气湍流模型对ｄ０进行了计算，说明了校正平移和倾斜对自适应光学系统的重要性。 In the adaptive optics system using laser stellar star, the non-isotropy of focal length is the main limitation to the performance of adaptive optics system. The variance of residual wavefront distortion is derived by the aperture filter function of turbulence detection. Based on this, the effective diameter d0 of the imaging system is deduced. Based on the atmospheric turbulence model measured by Kunming and Xinglong, d0 is calculated, which shows the importance of correcting the translation and tilt to the adaptive optics system.