The detectability of See-To-Ground(STG) wavebands of the infrared warning satellite computational models were constructed, and the possible wavebands range and the role of this STG waveband in missile early warning system were studied by simulation on the basis of those models. Firstly, a series of models for the infrared radiation model of solid and liquid rocket plume, the atmospheric background radiation, the point target radiation flux apparent contrast spectrum, the system noise and the lowest detection height were established. Secondly, the apparent contrast spectrum of solid and liquid rockets plume were analyzed and the STG band was deemed to be 2.86-3.0 μm. Thirdly, the detection ability was preliminarily investigated based on the analysis of the rule by which the apparent contrast spectrum of solid and liquid rockets plume varied according to the height. Finally, the detectability of SBIRS-GEO warning satellite at STG band was studied thoroughly, based on the analysis of the first detection height under different condition. The research shows that the STG band possesses superior early warning ability to solid rockets, and weaker early warning ability to liquid rockets.