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.