I discuss the mechanism of nonresonant Higgs pair production at the LHC through gluon fusion in the framework of the type-II two-Higgs-doublet model with vectorlike quark fermions in the alignment limit. We found that the presence of vectorlike quarks in the loops lead to enhancement of the total cross section. On the other hand, there is also a non-trivial change on the shape of the kinematical distributions through bump-like structure. This can be seen in both the transverse mass of the Higgs boson and the invariant mass of the system of the Higgs bosons. At the reconstruction level, we found that these features do not change and furthermore the acceptance times the efficiency is larger than the case of the SM Higgs pair production with or without anomalous Higgs triple couplings.
