  In this work, we update the catalog of M-giant stars from the low-resolution
spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope
(LAMOST) Data Release 9. There are 58,076 M giants identified from the
classification pipeline with seven temperature subtypes from M0 to M6. The 2471
misclassified non-M-giant stars are white dwarf binaries, early types, and M
dwarfs. And the contamination rate is 4.2$\%$ in the M-giants sample. A total
of 372 carbon stars were identified by CaH spectral indices, and were further
confirmed by the LAMOST spectra. We update the correlation between the
$(W1-W2)_0$ color and [M/H] from APOGEE DR17. We calculate the radial
velocities of all M giants by applying cross-correlation to the spectra between
8000 and 8950 \AA with synthetic spectra from ATLAS9. Taking star distances
less than 4 kpc from Gaia EDR3 as the standard, we refitted the photometric
distance relation of M giants. And based on our M-giant stars, we select a
group of Sagittarius stream members, whose sky and 3D velocity distributions
are well consistent with K-giant Saggitarius stream members found in Yang et
al. With our M giants, we find that the disk is asymmetric out to R = 25 kpc,
which is 5 kpc further out than detected using K giants.
