Based on the inherent molecular structure characteristics of the OH radicals, the energy level distribution, the transition frequency and Einstein spontaneous emission transition probability are systematically analyzed and numerically studied. Meanwhile, combined with the spectra experiments, the natural broadening, collision broadening, Doppler broadening and instrumental broadening effects on spectral line shape are analyzed. The dependence of the spectral profile on the rotational temperature, the vibrational temperature, and the spectral function are numerically explored in certain ranges. The corresponding numerical results are also discussed for the emission spectra thermometry, which provides a theoretical basis for the emission thermometry. In experimental, the emission spectra of OH (A2Σ+→X2Πr) system of the hydrogen flames are recorded by the optical multi-channel analyzer and studied. By the fitting of the experimental spectra to the numerically calculated spectra, the corresponding rotational and vibrational temperatures of the hydrogen flames are determined, respectively.