With the development of multispectral, hyperspectral and hyperspectral detection technology, the technology of detecting and recognizing the detailed spectral radiation characteristics emitted by the space target became increasingly mature. A model for calculating the fine spectral effective radiation of the space target was established. Considering the influence of terrain and atmospheric environment on the spectral effective radiation of the space target, the temperature and fine spectral effective radiation of each surface of the space target under the traditional method and two typical terrain conditions were calculated respectively. The effective radiation intensity of the space target at 3-5 μm and 8-14 μm bands was analyzed with respect to wavelength. Finally, the radiation characteristics of space target at 8.69-9.00 μm detection band under different terrain conditions were analyzed. The results show that the terrain conditions had a great influence on the temperature and effective radiation of the space target, especially the surface albedo had a great influence on the solar radiation reflected by the earth. For the surface of the space target facing the earth, the maximum temperature difference could reach 69.2 K under the two typical conditions, and the deviation of spectral effective radiation emittance reached 7.002 W/(m2·μm).