The invention relates to a spectral standardization-based coal quality on-line detection method, which can be used for coal quality on-line detection based on a laser induced plasma spectra principle. In the method, a calibrating model is established by using the intensity of an atomic characteristic spectral line after spectral standardization as a vertical coordinate and using the concentrationof an element corresponding to the atomic characteristic spectral line as a horizontal coordinate. When the coal with unknown components is detected, the concentration of an element to be tested can be obtained according to the calibrating model after the spectral standardization. In the method, plasma temperature, electronic density, density ratio of ion to atom of the same element and a boltzmann's law are taken into consideration, so that the fluctuation of experiment parameters is compensated and the measuring precision is improved. The method can also be applied to the similar occasions requiring on-line real-time detection of chemical components.