Based on the measured spectral reflectivity and the spectral signature of atmosphere radiation, a waveband selection method is given to detect target outside atmosphere. The reflection spectra of the samples and standard board are measured, and the spectral reflectivity of the samples is obtained. In order to improve the target identification, waveband selection is proceeded after considering the target radiation, the spectral reflectivity, the background radiation, the target-background contrast, the transmittance of slanting path and so on. The typical spectral characteristics of the above considerations are calculated by the atmospheric transmission model software MODTRAN and analyzed. The results show that 0.76～0.90 μm is the optimal detection waveband for target with yellow aluminium-coated polyester thin-film, and 0.52～0.60 μm for target with silver aluminium-coated polyester thin-film.