  We study the Wannier-Stark (WS) localization in one-dimensional
amplitude-chirped lattices with the $j$th onsite potential modulated by a
function $Fj\cos(2\pi \alpha j)$, where $F$ is the external field with a period
determined by $\alpha=p/q$ ($p$ and $q$ are coprime integers). In the Hermitian
(or non-Hermitian) systems with real (or imaginary) fields, we can obtain real
(or imaginary) WS ladders in the eigenenergy spectrum. In most cases with $q
\geq 2$, there are multiple WS ladders with all the eigenstates localized in
the strong field limit. However, in the lattices with $q=4$, the
energy-dependent localization phenomenon emerges due to the presence of both
spatially periodic and linearly increasing behaviors in the onsite potential.
About half the number of eigenstates are gathered at the band center and can
extend over a wide region or even the full range of the lattice, even when the
field becomes very strong. Moreover, in the non-Hermitian lattices with odd
$q$, some of the WS ladders become doubly degenerate, where the eigenstates are
evenly distributed at two neighboring sites in a wide regime of field strength.
Our work opens an avenue for exploring WS localization in both Hermitian and
non-Hermitian amplitude-chirped lattices.
