Based on detailed analysis of the frequency characteristics of routinely configured DTGS detector module, a smart correction method for FTIR spectrometer acquired response spectra of photodetectors has been proposed, and validated through different types of mid-infrared photovoltaic detectors operated at different temperatures. Results show that some weaknesses and limitations of previous correction methods are overcome, the instrument function of the FTIR spectrometers could be simply obtained by using DTGS acquired background without further fitting, and the correction process is easier. Furthermore, severe interference effects of the strong absorption features of CO2 and H2O at mid-infrared band could be suppressed dramatically. The applicability and universality of the method have been approved for scan speeds frequently used in experiments. This correction method is applicable from NIR, MIR and extending to FIR of wavelength above 100 μm for multitudinous photodetectors.