  We study B_s-\bar{B}_s mixing in grand unified SO(10), SU(5) models where the
mixings among the second and third generation squarks arise due to the
existence of flavor violating sources in the Dirac and Majorana couplings which
are responsible for neutrino mixings. We find that when the branching ratio of
tau->mu gamma decay is enhanced to be around the current experimental bound,
B_s-\bar{B}_s mixing may also contain large contribution from supersymmetry in
the SO(10) boundary condition. Consequently, the phase of B_s-\bar{B}_s mixing
is large (especially for small tan beta and large scalar mass m_0) and can be
tested by measuring CP asymmetries of B_s decay modes.
