  We propose a scheme to exhibit Stern-Gerlach (SG) deflection of
high-dimensional vector optical soliton (VOS) at weak-light level in a cold
atomic gas via electromagnetically induced transparency. We show that the
propagating velocity and generation power of such VOS can be reduced to
$10^{-6}\,\,c$ ($c$ is light speed in vacuum) and lowered to magnitude of
nanowatt, respectively. The stabilization of the VOS may be realized by using
an optical lattice formed by a far-detuned laser field, and its trajectory can
be deflected significantly by using a SG magnetic field. Deflection angle of
the VOS can be of magnitude of $10^{-3}$ rad when propagating several
millimeters. Different from atomic SG deflection, deflection angle of the VOS
can be distinct for different polarization components and can be manipulated in
a controllable way. The results obtained can be described in terms of a SG
effect for the VOS with quasispin and effective magnetic moment.
