The methods of pattern recognition theory are applied to identification of lines in the molecular rovibrational spectra. The method proposed is based on recogniting systems of spectral lines meeting the Ridberg-Rits combination rule and most close to those calculated using some estimates of rotational constants and transition moments. The expert system was created for analysis of spectra of asymmetric top molecules. This system can automatically seek and assign spectral lines. It is based on the Watson effective vibrational Hamiltonian, the Pade-Borel approximation, generation functions, and allows for the resonance interactions. To construct the decision rule during learning, the system uses the method of potential functions that allows the reconstruction of the decision rule to be done using learning sequence.