In order to improve the stability and resolution of equivalent temperature and area, an infrared multi-spectral design method was proposed based on feature parameter extraction of point target. Firstly, the anti-error ability of multi bands was simulated by multi spectral design criteria, and the influencing factors of spectrum design were determined. According to the noise analysis of the ground-based infrared radiation measurement system, the conditions for the best working performance of the middle wave and long wave photodetectors were determined. Finally, the spectral distribution was determined according to the estimation of the band SNR and the infrared atmospheric window. The performance analysis results show that the designed spectrum can make the medium wave and the long wave work together in the case of various changes of the target, greatly improving the stability and resolution of the equivalent temperature and the equivalent area.