  We consider the exclusive decay $B\to J/\psi K$ using the QCD-improved
factorization method in the heavy quark limit. It is shown that the decay
amplitude is factorizable in this limit and nonfactorizable contributions are
calculable from first principles in perturbation theory. Also the spectator
contributions at order $\alpha_s$ are finite and suppressed in the heavy quark
limit. We present the result at next-to-leading order in strong interaction,
and leading order in $1/m_b$ in the heavy quark limit.
