  The production of $J/\psi$ and $\Upsilon$ mesons decaying into dimuon final
state is studied at the LHCb experiment, with rapidity in the range of (1.5,
4.0) or (-5.0, -2.5) in proton-lead collisions at a nucleon-nucleon
centre-of-mass energy $\sqrt{s_{NN}}$ = 5 TeV, based on a data sample
corresponding to an integrated luminosity of 1.6 /fb. The nuclear modification
factor and forward-backward production ratio are determined for prompt
$J/\psi$, $J/\psi$ from b-hadron decay and $\Upsilon(1S)$ mesons in study of
the cold nuclear matter effects.
