In view of direct temperature inversion by broadband absorbance, the individual and comprehensive influence of spectral noise and spectral parameter error on temperature inversion accuracy at a temperature range of 300-2000 K by numerical simulation is analyzed. When only spectral noise exists, the noise with an amplitude of ±0.005 is taken as a minimum noise, and the spectral noise whose amplitude is increased from ± 0.005 to ±0.1 is added. When the noise amplitude is ±0.1, the maximum standard deviation of temperature is 46.58 K @ 1700 K. In order to make the standard deviation less than 10 K, the spectral noise amplitude should be controlled within ± 0.02. when only spectral parameter error exists, the spectral parameter error of calibrated strong absorption lines and uncalibrated weak absorption lines is set to 1% and 10%-50%, respectively, and the maximum standard deviation of temperature is 7.77 K @1300 K (an error combination of 1% and 40%). The line intensity error has the greatest influence on temperature inversion, and thus the calibrated error of the line intensity should be controlled within 1% as far as possible. When spectral noise and spectral parameter error coexist, spectral noise has a greater impact on the temperature measurement accuracy, and the absorption signal with a better signal noise ratio can reduce the influence of spectral noise in the actual measurement process.