The flame temperature measurement is one of important operations in combustion process control. Based on the theory of molecular spectroscopy, spectral line intensity distribution of OH radicals in the electronic band of [A2∑+X2∏] for several rotational and vibrational temperatures under the condition of instrument broadening of 0.07 nm is calculated. Experiments to measure spectral emissions of flames generated by alcohol lamp are carried out with a grating spectrometer. Spectral emissions of OH radicals at certain height of flames are gained. Through comparative analysis of theoretical and experimental spectroscopy, it is found that combustion temperature of alcohol lamp flame at certain height is about 2 600 K. And experimental errors and their causes are analyzed.