  We review some recent progress in understanding various exclusive double
charmonium production processes at $B$ factories, within the nonrelativistic
QCD factorization framework. First we investigate the impact of the joint
perturbative and relativistic correction on the process that has attracted a
great amount of attention in the past decade, $e^+e^-\to J/\psi+\eta_c$. We
then briefly discuss the phenomenological implication of the next-to-leading
order perturbative correction to the processes $e^+e^-\to J/\psi+\chi_{c0,1,2}
(\eta_{c2})$. We further emphasize a novel theoretical challenge, which is
recently discovered by applying the NRQCD factorization approach to the
helicity-suppressed hard exclusive reactions involving heavy quarkonium.
