To overcome the limitation of CR-39 at high dose region where large number of tracks are overlapped, the FTIR spectroscopic technique can be implemented for dose estimation. In the present work, CR-39 detectors were irradiated with alpha particles from ²³⁹Pu source having known doses up to 5.12 Gy. The detectors were subjected to chemical etching in steps of 1 h and subsequently FTIR spectra were recorded. Three strong bands i.e., 1800–1675 cm⁻¹, 1350–1150 cm⁻¹ and 810–760 cm⁻¹ in the FTIR spectra were analysed to study the effect of etching and dose on the peak absorbance of these bands. The peak absorbance was found to decrease with the dose as well as with etching duration and the saturation effect in the peak absorbance was observed above 3 h etching. Etching duration of 2 h was found to be optimal etching time where the linear response was observed up to 5.12 Gy. Furthermore, the threshold for dose estimation by the FTIR spectroscopic technique was observed to be 0.41 Gy, above which this technique can be used. Empirical relations correlating the peak absorbance and dose were generated which can be used as calibration factors for dose estimation in the range 0.41–5.12 Gy using the peak intensity in FTIR spectrum of CR-39 detector.