  We present a perturbative QCD factorization formula for substructures of an
energetic Higgs jet, taking the energy profile resulting from the $H\to b\bar
b$ decay as an example. The formula is written as a convolution of a hard Higgs
decay kernel with two $b$-quark jet functions and a soft function that links
the colors of the two $b$ quarks. We derive an analytical expression to
approximate the energy profile within a boosted Higgs jet, which significantly
differs from those of ordinary QCD jets. This formalism also extends to boosted
$W$ and $Z$ bosons in their hadronic decay modes, allowing an easy and
efficient discrimination of fat jets produced from different processes.
