Abstract: Near space has unique application value, and strengthening the development and utilization has become a new focus of competition among major countries. Establishing a comprehensive atmospheric water vapor forward model for near space and conducting forward simulations are the important basis for high-precision detection of atmospheric water vapor. Using the SCIATRAN radiative transfer model, the study establishes an atmospheric water vapor forward model, simulates the satellite observations at an orbital altitude of 500 km to carry out limb observation of the atmospheric water vapor in the altitude range of 20-100 km in the atmosphere, and obtains the atmospheric water vapor absorption spectra in the band of 1 355-1 365 nm. The simulation results show that the tangent altitude has a significant influence on the radiative and absorption characteristics of atmospheric water vapor spectra. Meanwhile, the comparison of the simulation results between SCIATRAN and MODTRAN shows that under the same observation conditions, the correlation coefficient of the atmospheric water vapor absorption spectral data obtained by the two radiative transfer models is 0.959 4, and the difference in the absorption line value is lower than 0.2, which verifies the correctness and feasibility of the simulation of atmospheric water vapor in near space by using the SCIATRAN radiative transfer model. In addition, the comparison of the simulation results of the two radiative transfer models at different resolutions shows that the SCIATRAN radiative transfer model is more suitable as a forward model for the high-precision detection of atmospheric water vapor in near space.