  The charge density wave (CDW), as a hallmark of vanadium-based kagome
superconductor AV3Sb5 (A = K, Rb, Cs), has attracted intensive attention.
However, the fundamental controversy regarding the underlying mechanism of CDW
therein persists. Recently, the vanadium-based bi-layered kagome metal ScV6Sn6,
reported to exhibit a long-range charge order below 94 K, has emerged as a
promising candidate to further clarify this core issue. Here, employing
micro-focusing angle-resolved photoemission spectroscopy ({\mu}-ARPES) and
first-principles calculations, we systematically studied the unique CDW order
in vanadium-based bi-layered kagome metals by comparing ScV6Sn6 with its
isostructural counterpart YV6Sn6, which lacks a CDW ground state. Combining
ARPES data and the corresponding joint density of states (DOS), we suggest that
the VHS nesting mechanism might be invalid in these materials. Besides, in
ScV6Sn6, we identified multiple hybridization energy gaps resulting from
CDW-induced band folding, along with an anomalous band dispersion, implying a
potential electron-phonon coupling driven mechanism underlying the formation of
the CDW order. Our finding not only comprehensively maps the electronic
structure of V-based bi-layer kagome metals but also provide constructive
experimental evidence for the unique origin of CDW in this system.
