介绍了光学追迹计算中采用的空气折射率公式，分析了在水平和垂直两种检测情形下，不同曲率半径球面反射镜因空气温度分层导致的像质变化。对Φ1.5 m 、离轴量为12 m 近抛物面拼接子镜在水平和垂直状态检验时受温度梯度影响情况进行了计算和分析。最后在上述两种状态下仿真计算了温度梯度分布对Φ4 m，焦比f /2的大口径抛物面反射镜的影响情况。结果显示，一般来说水平检验光路像质变化远大于垂直检验，其中大口径快焦比的抛物面镜垂直检测空气温度分层因素的影响结果也需考虑和控制。

The formula of air refractive index used in this paper for optical trace computing is described in detail. Following the changing of image quality of spherical mirrors with different R is analyzed caused by air temperature layered in horizontal and vertical testing cases. The temperature gradient effects for off-axis near parabolic segment with Φ1.5 m, off-axis length 12 m are calculated and analyzed in horizontal and vertical test status. Finally, the influence of image quality by air temperature gradient distribution for large parabolic mirror with aperture Φ4 m, focal ratio f/2 with the states above mentioned is calculated and simulated. The results above all indicate that, in general, the influence level for image quality in horizontal test is much greater than vertical case, moreover, the air temperature factors should be considered in vertical optical testing in large aperture and fast focal ratio parabolic testing.