The acquisition of aircraft altitude information is crucial for aviation safety and traffic control applications.Currently, it is difficult to obtain the altitude information of aircraft only through passive remote sensing methods. By combining atmospheric parameters retrieval and high-sensitivity infrared detection technology, space-borne remote sensing platforms can achieve accurate measurement of target thermal radiation information and have the potential for quantitative observation of aircraft characteristic information. 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 is 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 aircraft at different altitudes and flight states under different atmospheric conditions can be obtained by simulating. Thirdly, target spectral information can be extracted from remote sensing images and the altitude information can be estimated with 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.Key words: thermal infrared remote sensing, altitude estimate, spectral angle matching, large aircraft