  We predict the upper limit of the branching ratio (BR) of the lepton flavor
violation (LFV) of Z boson decaying into
\left(\mathrm{Z\longrightarrow}\mathrm{e}^\mathrm{\mp}\mathrm{\ }
\mathrm{\tau}^\mathrm{\pm}\right),\left(\mathrm{Z\longrightarrow}\mathrm{\mu}^\mathrm{\mp}\mathrm{\tau}^\mathrm{\pm}\right),\left(\mathrm{Z\rightarrow}{\mathrm{\
e}}^\mathrm{\pm}\mathrm{\mu}^\mathrm{\mp}\right) .This study is conducted in
the context of the Constrained Minimal Supersymmetric Standard Model (CMSSM)
which is extended by Seesaw type-II model. The decay rate of LFV processes is
calculated in the CMSSM model at the grand unified scale ~2\times{10}^{16} GeV.
The upper limit predicted results of LFV processes of branching ratio (BR) of Z
boson decays for the three decay channels are found to be in the order of
\mathrm{~1\times}{\mathrm{10}}^{\mathrm{-9}},
\mathrm{~1\times}{\mathrm{10}}^{\mathrm{-9}}and
\mathrm{~1\times}{\mathrm{10}}^{\mathrm{-10}} respectively, which corresponds
with the predicted sensitivity of the future colliders (FCC-ee/CEPC).
