  Context. White dwarf-main sequence (WDMS) binaries are used to study several
different important open problems in modern astrophysics.
  Aims. The Sloan Digital Sky Survey (SDSS) identified the largest catalogue of
WDMS binaries currently known. However, this sample is seriously affected by
selection effects and the population of systems containing cool white dwarfs
and early-type companions is under-represented.Here we search for WDMS binaries
within the spectroscopic data release 1 of the LAMOST (Large sky Area
Multi-Object fiber Spectroscopic Telescope) survey. LAMOST and SDSS follow
different target selection algorithms. Hence, LAMOST WDMS binaries may be drawn
from a different parent population and thus help in overcoming the selection
effects incorporated by SDSS on the current observed population.
  Methods. We develop a fast and efficient routine based on the wavelet
transform to identify LAMOST WDMS binaries containing a DA white dwarf and a M
dwarf companion, and apply a decomposition/fitting routine to their LAMOST
spectra to estimate their distances and measure their stellar parameters,
namely the white dwarf effective temperatures, surface gravities and masses,
and the secondary star spectral types.
  Results. We identify 121 LAMOST WDMS binaries, 80 of which are new
discoveries, and estimate the sample to be \sim90 per cent complete. The LAMOST
and SDSS WDMS binaries are found to be statistically different. However, this
result is not due to the different target selection criteria of both surveys,
but likely a simple consequence of the different observing conditions. Thus,
the LAMOST population is found at considerably shorter distances (\sim50-450
pc) and is dominated by systems containing early-type companions and hot white
dwarfs. (abridged)
