  The spectroscopic sky survey carried out by the Large Sky Area Multi-Object
Fiber Spectroscopic Telescope (LAMOST) provides the largest stellar spectra
library in the world until now. A large number of new DA white dwarfs had been
identified based on the LAMOST spectra. The effective temperature ($T_{\rm
eff}$) and surface gravity ($\log g$) of most DA white dwarfs were determined
and published in the catalogs, e.g. Zhao et al. (2013), Rebassa-Mansergas et
al. (2015), Gentile Fusillo et al. (2015) and Guo et al. (2015). We selected ZZ
Ceti candidates from the published catalogs by considering whether their
$T_{\rm eff}$ are situated in the ZZ Ceti instability strip. The follow-up
time-series photometric observations for the candidates were performed in 2015
and 2016. Four stars: LAMOST J004628.31+343319.90, LAMOST J062159.49+252335.9,
LAMOST J010302.46+433756.2 and LAMOST J013033.90+273757.9 are finally confirmed
to be new ZZ Ceti stars. They show dominant peaks with amplitudes rising above
the 99.9% confidence level in the amplitude spectra. As LAMOST
J004628.31+343319.90 has an estimated mass of $\sim$ 0.40 $M_{\odot}$ and
LAMOST J013033.90+273757.9 has a mass of $\sim$ 0.45 $M_{\odot}$ derived from
their $\log g$ values, these two stars are inferred to be potential helium-core
white dwarfs.
