  We report the Neutrino-less Double Beta Decay (NLDBD) search results from
PandaX-II dual-phase liquid xenon time projection chamber. The total live time
used in this analysis is 403.1 days from June 2016 to August 2018. With
NLDBD-optimized event selection criteria, we obtain a fiducial mass of 219 kg
of natural xenon. The accumulated xenon exposure is 242 kg$\cdot$yr, or
equivalently 22.2 kg$\cdot$yr of $^{136}$Xe exposure. At the region around
$^{136}$Xe decay Q-value of 2458 keV, the energy resolution of PandaX-II is
4.2%. We find no evidence of NLDBD in PandaX-II and establish a lower limit for
decay half-life of 2.4 $ \times 10^{23} $ yr at the 90% confidence level, which
corresponds to an effective Majorana neutrino mass $m_{\beta \beta} < (1.3 -
3.5)$ eV. This is the first NLDBD result reported from a dual-phase xenon
experiment.
