  Lithium is a fragile but crucial chemical element in the universe, exhibits
interesting and complex behaviors. Thanks to the massive spectroscopic data
from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)
medium-resolution survey (MRS), we can investigate the lithium abundances in a
large and diverse sample of stars, which could bring vital help to study the
origin and evolution of lithium. In this work, we use the Li 6,707.8 {\AA} line
to derive the lithium abundance through a template-matching method. A catalog
of precise lithium abundance is presented for 795,384 spectra corresponding to
455,752 stars from the LAMOST MRS Data Release (DR) 9. Comparing our results
with those of external high-resolution references we find a good consistency
with a typical deviation of {\sigma} A(Li) ~ 0.2 dex. We also analyze the
internal errors using stars that have multiple LAMOST MRS observations, which
will reach as low as 0.1 dex when the signal-to-noise ratio (S/N) of the
spectra > 20. Besides, our result indicates that a small fraction of giant
stars still exhibit surprisingly high amount of lithium contents, and 967 stars
are identified as Li-rich giants with A(Li) > 1.5 dex, accounting for ~ 2.6% of
our samples. If one takes into account the fact that nearly all stars deplete
lithium during the main sequence, then the fraction of Li-rich stars may exceed
2.6% much. This new catalog covers a wide range of stellar evolutionary stages
from pre-main sequence to giants, and will provide help to the further study of
the chemical evolution of lithium.
