  The $B_c(^1S_0)$ meson to S-wave Charmonia transition form factors are
calculated in next-to-leading order(NLO) accuracy of Quantum
Chromodynamics(QCD). Our results indicate that the higher order corrections to
these form factors are remarkable, and hence are important to the
phenomenological study of the corresponding processes. For the convenience of
comparison and use, the relevant expressions in asymptotic form at the limit of
$m_c\rightarrow0$ for the radiative corrections are presented.
