<p>Accurate temperature measurement is a crucial step in predicting and managing the aerodynamic heating during Mars entry and Earth reentry. These processes often occur at extremely high temperatures and pose challenges for quantitative measurements. A 1-µs time-resolved laser absorption technique was developed for simultaneous and time-dependent temperature and CO-concentration measurements over 3000–6000 K by adopting the P(0, 21) and P(2, 15) lines. To achieve quantitative measurement, the line strengths and Ar-broadening parameters were calibrated within 3030–5980 K. A “W”-shaped path-amplified strategy was used to increase the absorption features of the two lines during the calibration process. Validation experiments were conducted at 3040–5970 K to verify the accuracy of the technique. The new technique was then applied for simultaneous and time-resolved temperature and CO-concentration measurements during the CO₂ dissociation process to further demonstrate the feasibility of the developed technique. The temperature-dependent CO₂ absorption cross-sections at line centers of the two lines were calibrated within 2040–5870 K. The CO₂ absorption interferences were quantified and subtracted from the measured laser absorbances. The measured results (referring to temperature and CO concentration) were generally consistent with the predictions from the kinetics mechanisms in the literature, highlighting the applicability of the developed technique for temperature measurements and CO₂ dissociation studies within the investigated temperature range.</p>