A method of attitude estimation of a spotted target. The method includes an offline training and an online estimation. The offline training includes establishing a three-dimensional geometric model of a target, performing region division according to the structure of the target, establishing an object-space temperature distribution model for each region of the target, establishing an infrared radiation transmission model of an intra-atmospheric target in six attitudes in observation by a detection system, constructing an image-space radiant energy model of the target in the six attitudes using the object-space temperature distribution model and the infrared radiation transmission model, and performing simulation calculation to obtain an infrared spectral curve of the spotted target regarding wavelength versus image-space-radiant-energy-of-target, so as to establish a mapping database regarding target-attitude versus spectrum.