  Based on luminosity contributions, we develop a spectroscopic modelling
method to derive atmospheric parameters of component stars in binary systems.
The method is designed for those spectra of binaries which show double-lined
features due to the radial velocities differences between the component stars.
We first derive the orbital parameters and the stellar radii by solving the
light and radial velocity curves. Then the luminosity contributions in
different phases can be calculated. The synthesised double-lined spectra model
is constructed by superposing theoretical single-star spectra according to the
luminosity contributions. Finally, we derive the atmospheric parameters of each
component star by the model fitting method. For multi-epoch double-lined
spectra observed by the Large sky Area Multi-Object Spectroscopic Telescope
(LAMOST) Medium Resolution Survey ($R \sim 7500$), our method gives robust
results for detached eclipsing binary systems observed in different orbital
phases. Furthermore, this method can also be applied to other spectroscopic
data with different resolutions as long as the systems are detached eclipsing
binaries with nearly spherical stars.
