We studied the boundary layer effects on flame temperature measurements using line-of-sight (LOS) absorption spectroscopy. The primary objective is to quantify the measurement uncertainty of the LOS-determined temperature, which is influenced by the thermal and species boundary layers existing in standard laminar premixed flames. The boundary layer thickness (δ), central flame temperature (Tc) and species concentration (Xc) are the major factors investigated in this work. Typical absorption lines of H2O in the wavelength range of...