The acquisition of aircraft altitude information is crucial for the aviation safety and traffic control applications. Infrared remote sensing technology can accurately measure the thermal radiation information of targets, which means the potential for quantitative observation of certain characteristics of aircraft target. A method for estimating the altitude of airborne targets based on infrared multi-channel feature matching is proposed in this paper. Firstly, a thermal infrared radiation characteristic observation model of aircraft is established, which based on the thermal infrared radiation characteristics of large aircraft and atmospheric radiative transfer models. Secondly, based on the observation model, a spectral database of aircrafts at different altitudes and flight states under different atmospheric condition can be obtained by simulating. Thirdly, target spectral information can be extracted from remote sensing images and the altitude information can be estimated with using spectral angle matching (SAM). Finally, verification and analysis were completed using simulation data and SDGSAT-1 in-orbit data. The results indicate that the proposed method can achieve kilometer-level estimation accuracy for aircraft at cruising altitude. This method provides a new solution for estimating the altitude of aircraft and has important application potential.