  A model of low-frequency quasi-periodic oscillations (LFQPOs) of black hole
X-ray binaries (BHXBs) is proposed based on the perturbed magnetohydrodynamic
(MHD) equations of accretion disk. It turns out that the LFQPOs frequencies of
some BHXBs can be fitted by the frequencies of the toroidal Alfv\'en wave
oscillation corresponding to the maximal radiation flux. In addition, the
positive correlation of the LFQPO frequencies with the radiation flux from
accretion disk is well interpreted.
