  The Jiangmen Underground Neutrino Observatory (JUNO) is designed to study
neutrino mass hierarchy and measure three of the neutrino oscillation
parameters with high precision using reactor antineutrinos. It is also able to
study many other physical phenomena, including supernova neutrinos, solar
neutrinos, geo-neutrinos, atmosphere neutrinos, and so forth. The central
detector of JUNO contains 20,000~tons of liquid scintillator (LS) and about
18,000 20-inch photomultiplier tubes (PMTs), which is the largest liquid
scintillator one under construction in the world up today. The energy
resolution is expected to be 3\%/$\sqrt{E(MeV)}$. To meet the requirements of
the experiment, an algorithm of vertex reconstruction, which takes into account
time and charge information of PMTs, has been developed by deploying the
maximum likelihood method and well understanding the complicated optical
processes in the liquid scintillator.
