  The Jiangmen Underground Neutrino Observatory (JUNO) is a multi-purpose
neutrino experiment. One of the main goals is to determine the neutrino mass
ordering by precisely measuring the energy spectrum of reactor antineutrinos.
For reactor antineutrino detection, cosmogenic backgrounds such as
$^9$Li/$^8$He and fast neutrons induced by cosmic muons should be rejected
carefully by applying muon veto cuts, which requires good muon track
reconstruction. With a 20~kton liquid scintillator detector, simulation shows
the proportion of muon bundles to be around 8\% in the JUNO, while its
reconstruction is rarely discussed in previous experiments. According to the
charge response of the PMT array, this paper proposes an efficient algorithm
for muon bundle track reconstruction. This is the first reconstruction of muon
bundles in a large volume liquid scintillator detector. Additionally, the
algorithm shows good performance and potential in reconstruction for both
single muon and double muons. The spatial resolution of single muon
reconstruction is 20~cm and the angular resolution is $0.5^\circ$. As for
double muon reconstruction, the spatial resolution and angular resolution could
be 30~cm and $1.0^\circ$, respectively. Moreover, this paper has also discussed
muon classification and veto strategy.
