  We examine the implication of the 750 GeV diphoton resonance on the
two-Higgs-doublet model imposing various theoretical and experimental
constraints. The production rate of two-Higgs-doublet model is smaller than the
cross section observed at the LHC by two order magnitude. In order to
accommodate the 750 GeV diphoton resonance, we extend the two-Higgs-doublet
model by introducing additional Higgs fields, and focus on two different
extensions, an inert complex Higgs triplet and a real scalar septuplet. With
the 125 GeV Higgs being agreement with the observed data, the production rate
for the 750 GeV diphoton resonance can be enhanced to 0.6 fb for the former and
4.5 fb for the latter. The results of the latter are well consistent with the
750 GeV diphoton excess at the LHC.
