Aiming at the problems of composition complexity, low combustion efficiency and poor combustion stability of blast furnace gas, a temperature measurement method of blast furnace gas combustion field based on wavelength modulation spectroscopy(WMS) was proposed. WMS method has the characteristics of strong anti-noise ability, high measurement accuracy and high sensitivity. It was suitable for temperature measurement of blast furnace gas combustion field. Based on the measurement characteristics of tunable diode laser absorption spectroscopy, H2O was taken as the target gas, and its absorption spectral lines at 1 391.67 nm and 1 397.75 nm were selected. Two target absorption lines spectra were obtained by time division multiplexing of two lasers. The temperature measurement of blackbody furnace and flat flame combustion furnace were measured respectively for the experimental verification. The results show that the proposed detection scheme has high sensitivity to the temperature range of 500-2 000 K, and the linearity of the detection results is better than 99%. The field test verified that the system can meet the application of in-situ on-line measurement of blast furnace gas temperature, which lays a foundation for subsequent combustion optimization and energy saving and emission reduction.