We demonstrate absorption spectroscopy of water vapor for the determination of gas temperature. An adaptive dual-comb detection system is utilized to obtain precise spectroscopic data in a broadband range from 7143 to 7240 cm^?1 with a spectral resolution of 0.049 cm^?1. The measured spectra are in accordance with the simulated results from the HITRAN (high-resolution transmission molecular absorption) database. Several measurements are investigated in the temperature range of 500–1000 K, revealing relative deviations of less than 5% compared to the thermocouple. This broadband and accurate adaptive dual-comb spectral detection method could be a powerful tool for non-invasive combustion diagnosis.