  The observability of charged Higgs $ H^{\pm} $ has been investigated at
future lepton collider by assuming type-I 2HDM, at a centre of mass energy $
\sqrt{s}=1.5$ TeV. The signal process chain is $ e^{+}e^{-} \rightarrow Z^{*}/
\gamma^{*}\rightarrow H^{+} H^{-}\rightarrow H W^{+} H W^{-}\rightarrow b
\overline{b} jjb \overline{b} jj$. The process proceed through virtual gamma
and Z-boson exchange in S-channel. Several benchmark points are selected and
events are analyzed to reconstruct the mass of charged Higgs bosons $ H^{\pm}
$. The value of $\tan\beta $ is kept relatively high to enhance the branching
ratio of $ H\rightarrow b\overline{b} $ to benefit the signal processes. The
main SM background processes produced is $ t\overline{t} $. Signal selection
and significance efficiencies are calculated at integrated luminosities of $100
fb^{-1} $ and $ 500 fb^{-1} $. The reconstructed and corrected mass of charged
Higgs bosons $ H^{\pm} $ is determined. Through analyzing the results, it is
demonstrated that charged Higgs bosons can be discovered through pair
production process via its bosonic decays. This study is supposed to provide
the experimentalists a good way to examine the Higgs bosons beyond SM, as well
as to check the validity of 2HDM models in considered parameter space.
