  Searching for compact objects (black holes, neutron stars, or white dwarfs)
in the Milky Way is essential for understanding the stellar evolution history,
the physics of compact objects, and the structure of our Galaxy. Compact
objects in binaries with a luminous stellar companion are perfect targets for
optical observations. Candidate compact objects can be achieved by monitoring
the radial velocities of the companion star. However, most of the spectroscopic
telescopes usually obtain stellar spectra at a relatively low efficiency, which
makes a sky survey for millions of stars practically impossible. The efficiency
of a large-scale spectroscopic survey, the Large Sky Area Multi-Object Fiber
Spectroscopy Telescope (LAMOST), presents a specific opportunity to search for
compact object candidates, i.e., simply from the spectroscopic observations.
Late-type K/M stars are the most abundant populations in our Galaxy. Owing to
the relatively large Keplerian velocities in the close binaries with a
K/M-dwarf companion, a hidden compact object could be discovered and
followed-up more easily. In this study, compact object candidates with
K/M-dwarf companions are investigated with the LAMOST low-resolution stellar
spectra. Based on the LAMOST Data Release 5, we obtained a sample of $56$
binaries, each containing a K/M-dwarf with a large radial velocity variation
$\Delta V_{\rm R} > 150~{\rm km~s}^{-1}$. Complemented with the photometric
information from the Transiting Exoplanet Survey Satellite, we derived a sample
of $35$ compact object candidates, among which, the orbital periods of $16$
sources were revealed by the light curves. Considering two sources as examples,
we confirmed that a compact object existed in the two systems by fitting the
radial velocity curve. This study demonstrates the principle and the power of
searching for compact objects through LAMOST.
