According to the open literature, the characteristics of optics system about the visual angle, pixel number, spaceresolution and optics plus of the early warning detecting of space tracking and surveillance system are computed conversely. Base on the shortwave infrared radiation characteristics of target and background, wave band of the early warning detecting is analyzed, and a new viewpoint that early warning detector don’t work in low atmosphere transmittance of wave band for traditional early warning satellite is proposed. The results show that, under the high noise background, early warning detection unit can obtain the best detecting capability by taking strobe filtering measures to the waveband of high atmospheric transmittance.