  We study the blow-up criterion of smooth solutions to the 3D MHD equations.
By means of the Littlewood-Paley decomposition, we prove a Beale-Kato-Majda
type blow-up criterion of smooth solutions via the vorticity of velocity only,
i. e. $\sup_{j\in\Z}\int_0^T\|\Delta_j(\na\times u)\|_\infty dt$, where
$\Delta_j$ is a frequency localization on $|\xi|\approx 2^j$.
