  We investigate the imprint of dark energy on the kinetic Sunyaev-Zel'dovich
(kSZ) angular power spectrum on scales of $\ell=1000$ to $10000$, and find that
the kSZ signal is sensitive to the dark energy parameter. For example, varying
the constant $w$ by 20\% around $w=-1$ results in a $\gtrsim10\%$ change on the
kSZ spectrum; changing the dark energy dynamics parametrized by $w_a$ by
$\pm0.5$, a 30\% change on the kSZ spectrum is expected. We discuss the
observational aspects and develop a fitting formula for the kSZ power spectrum.
Finally, we discuss how the precise modeling of the post-reionization signal
would help the constraints on patchy reionization signal, which is crucial for
measuring the duration of reionization.
