大气层中气体浓度随海拔高度的指数衰减造成了大气折射率的不均匀分布。目标辐射在大气层中传播时，其辐射路径因折射作用变为曲线，而在求解目标距离时却是沿视在路径计算氧气吸收率，这使得氧气吸收被动测距中存在一个固有误差项，这里称之为折射吸收误差。为了分析折射吸收误差对氧气吸收被动测距的影响，分别计算目标辐射路径和视在路径的氧气浓度，并通过辐射路径和视在路径上吸收气体含量相等的方法，建立了不同视在天顶角的折射吸收误差和目标真实距离的关系。结果表明：相同天顶角下，折射吸收误差随路径长度增加而变大。天顶角小于90°时，折射吸收误差变化规律复杂，但能满足100 km以内的高精度近程测距和150 km以上的远程告警；天顶角大于90°时，折射吸收误差的变化规律简单且误差值很小，可实现全程高精度测距。因此该结论可为氧气吸收被动测距技术的误差修正提供一定的理论支持，同时也证明了该被动测距技术的适用性。

In the atmosphere, the exponential decay of the gas concentration with altitude causes the uneven distribution of atmospheric refractive index. With the propagation of the target radiation in the atmosphere, the radiation path turns into curves due to refraction. While getting target distance, oxygen absorption rate is calculated along the apparent path, which makes the existence of an intrinsic error term of oxygen absorption passive ranging named refraction absorption error. In order to analyze the impact of the refraction absorption error on passive ranging, the oxygen concentrations of the radiation path and apparent path are individually calculated. The relationship between the refraction absorption error and target real distance under different apparent zenith angles is established, through the method of making oxygen content of radiation path equaling that of apparent path. The results show that the refraction absorption error increases with the increasing of the path length at the same zenith angle. When zenith angle is less than 90°, the change of refraction absorption error is very complex, but could satify precision of shorten ranging under 100 km and long range alarm above 150 km. When zenith angle is greater than 90°, the change of the refraction absorption error is simple and the value of that is very small, and therefore precision ranging in the whole ranging can be realized. The conclusion can provide a theoretical support for the error correction of passive ranging technology based on oxygen absorption, and prove the applicability of the passive ranging technology.