  The QCD-like dark sector with GeV-scale dark hadrons has the potential to
generate new signatures at the Large Hadron Collider (LHC). In this paper, we
consider a singlet scalar mediator in the tens of GeV-scale that connects the
dark sector and the Standard Model (SM) sector via the Higgs portal. We focus
on the Higgs-strahlung process, $q\overline{q}'\rightarrow W^{\ast}\rightarrow
WH $, to produce a highly boosted Higgs boson. Our scenario predicts two
different processes that can generate dark mesons: (1) the cascade decay from
the Higgs boson to two light scalar mediators and then to four dark mesons; (2)
the Higgs boson decaying to two dark quarks, which then undergo a QCD-like
shower and hadronization to produce dark mesons. We apply machine learning
techniques, such as Convolutional Neural Network (CNN) and Energy Flow Network
(EFN), to the fat jet structure to distinguish these signal processes from
large SM backgrounds. We find that the branching ratio of the Higgs boson to
two light scalar mediators can be constrained to be less than $10\%$ at 14 TeV
LHC with $\mathcal{L} = 3000 fb^{-1}$.
