  The polarimetric measurement on the prompt phase of GRB 100826A shows that
the polarization angle changes $\sim 90^{\circ}$ between two adjacent time
intervals. We will show that this phenomenon can be naturally interpreted in
the framework of the magnetic-dominated jet (MDJ) model. The MDJ model suggests
that the bulk Lorentz factor of the outflow increases as $\Gamma\propto
r^{1/3}$, until reaching a saturated value $\Gamma_{\rm sat}$. Electrons move
in the globally ordered magnetic field advected by the jet from the central
engine and produce synchrotron photons. The polarized synchrotron photons
travel alone the jet direction and then collide with the cold electrons at the
front of the jet. After the Compton scattering process, these photons escape
from the jet and are detected by the observer locating slightly off-axis. If
photons are emitted before the bulk Lorentz factor saturates, the change of
polarization angle is a natural result of the acceleration of the outflow.
