  We have established and released a new stellar index library of the Ca II
Triplet, which serves as an indicator for characterizing the chromospheric
activity of stars. The library is based on data from the Large Sky Area
Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low-Resolution
Spectroscopic Survey (LRS) Data Release 9 (DR9). To better reflect the
chromospheric activity of stars, we have defined new indices $R$ and $R^{+}$.
The library includes measurements of $R$ and $R^{+}$ for each Ca II infrared
triplet (IRT) from 699,348 spectra of 562,863 F, G and K-type solar-like stars
with Signal-to-Noise Ratio (SNR) higher than 100, as well as the stellar
atmospheric parameters and basic information inherited from the LAMOST LRS
Catalog. We compared the differences between the 3 individual index of the Ca
II Triplet and also conducted a comparative analysis of $R^{+}_{\lambda8542}$
to the Ca II H&K $S$ and $R^+_{HK}$ index database. We find the fraction of low
active stars decreases with $T_{eff}$ and the fraction of high active first
decrease with decreasing temperature and turn to increase with decreasing
temperature at 5800K. We also find a significant fraction of stars that show
high activity index in both Ca II H&K and IRT are binaries with low activity,
some of them could be discriminated in Ca II H&K $S$ index and
$R^{+}_{\lambda8542}$ space. This newly stellar library serves as a valuable
resource for studying chromospheric activity in stars and can be used to
improve our comprehension of stellar magnetic activity and other astrophysical
phenomena.
