Abstract: The relation between aromaticity Obtained by the method of ~(13)C-NMR and absorbance at 1600 cm~(-1), 1460 cm~(-1), 1380 cm~(-1) obtained by the method of IR spectrometry is studied. The equation of spectral calculation for f_a is established which can be used for calculating f_a of asphalts and residual oil with higher accuracy, the errors being less than 5.5% and the values obtained in agreement with that calculated by B-L method.