Abstract: The calibration of the spectral responsivity of Fourier transform infrared(FTIR) spectrometer is the basis for accurate spectrum measurement. The spectral responsivity of FTIR spectrometer measurement system with high temperature blackbody infrared radiation characteristics, established at National Institute of Metrology, China(NIM), was calibrated based on piecewise linear calibration via the ThermoGage HT9500 high temperature reference blackbody furnace from NIM. A calculation model of the spectral responsivity calibration of FTIR measurement system was established and described. The infrared spectrum of the blackbody radiation source was measured in the temperature range of 1 273-1 973 K in the wavelength range of 1-14 m. The results indicate that the method of piecewise linear calibration is practicable. The measured infrared spectrum in the temperature range of 1 373-1 873 K in the wavelength range of 1-14 m was compared with the calculation which showed the signal divergence was less than 1%. The calculated temperature obtained by inverse calculation in this temperature region was compared with the actual temperature which showed the temperature divergence was less than 0.45%.