Abstract: In low SNR cases, the distinction between spatial point-target and interferences like decoys is still a very difficult problem, especial between the satellites target and mooring decoys. At that time decoys have the same orbit and similar shape with the spatial target, so that only could be used to distinguish the target is the radiation difference. However it is not easy to extract the multi-spectral radiation which is influenced by the detection distance and observation angle. In this paper, based on the characteristics that target and interferences like decoys and noise have different radiation intensity and radiation changing frequency, the concept of the equivalent blackbody temperature in several bands (EBTSB) was built. Then the calculation model of EBTSB was designed, which could effectively reduce the interference of the space environment and fully showed the radiation differences between point-target and interferences like decoys. Under noises interference, this model would produce calculation error, and different bands combinations had different error transmission capacity. In order to make error minimum, the best detection bands need to be determined. In this paper, the best detection dual-bands and the best detection multi-bands were obtained by calculating the trend of error with the band parameters under noises interference. By analyzing the results of the simulation experiments, the best detection dual-band will have 20% advantage and the best detection multi-bands will further reduce error 20%, which prove the correctness of the conclusions of this paper.