Remote sensing interferometer spectrometer Tensor37 was selected as measuring equipment based on spectrum characteristics of a middle infrared and long infrared dual-band (DF & CO2) laser on account of problems, such as blending of CO2 spectrum and the third level of DF spectrum, existing in grating monochromator and spectrophotometer. Simulating measurement and real measurement of dual-band laser spectrum were explored after validating blackbody radiation response function of Tensor37. Effective data including spectrum composition, peak fluctuation, wavelength accuracy and relative intensity were evaluated for calculating gain media parameters, optimizing operating parameters and infrared application of dual-band laser.