  388 hot subdwarf stars have been identified by using the Hertzsprung-Russell
(HR) diagram built from the second data release (DR2) of the Gaia mission. By
analyzing their observed LAMOST spectra, we characterized 186 sdB, 73 He-sdOB,
65 sdOB, 45 sdO, 12 He-sdO and 7 He-sdB stars. The atmospheric parameters of
these stars (e.g., T eff , log g, log(nHe/nH)) are obtained by fitting the
hydrogen (H) and helium (He) line profiles with synthetic spectra calculated
from non-Local Thermodynamic Equilibrium (non-LTE) model atmospheres. Among
these stars, we have 135 new identified hot subdwarfs which have not been
cataloged before. Although 253 stars appear in the catalog by Geier et al.
(2017) , but only 91 of them have atmospheric parameters. Together with the 294
hot subdwarf stars found by Lei et al. (2018), we identified 682 hot subdwarf
stars in total by using the Gaia HR-diagram and LAMOST spectra. These results
demonstrate the efficiency of our method to combine large surveys to search for
hot subdwarf stars. We found a distinct gap in our He-sdOB stars based on their
He abundance, which is also presented in extreme horizontal branch (EHB) stars
of the globular cluster (GC) {\omega} Cen. The number fraction of the sample
size for the two sub-groups is very different between the two counterparts.
However, the distinct gap between the H-sdB stars and He-sdOB stars in {\omega}
Cen is not visible in our sample. More interestingly, the He-sdB population
with the highest He abundance in our sample is completely missing in {\omega}
Cen. The discrepancy between our field hot subdwarf stars and the EHB stas in
{\omega} Cen indicate different origins for the two counterparts.

Solar and Stellar Astrophysics