  We have studied the polarized image of an equatorial emitting ring around a
4D Gauss-Bonnet black hole. Our results show that the effects of Gauss-Bonnet
parameter on the polarized image depend on the magnetic field configuration,
the observation inclination angle, and the fluid velocity. As the magnetic
field lies in the equatorial plane, the observed polarization intensity
increases monotonously with Gauss-Bonnet parameter in the low inclination angle
case, and its monotonicity disappears in the case with high inclination angle.
However, as the magnetic field is vertical to the equatorial plane, the
polarization intensity is a monotonously increasing function of Gauss-Bonnet
parameter in the high inclination angle case. The changes of the electric
vector position angle with Gauss-Bonnet parameter in both cases are more
complicated. We also probe the effects of Gauss-Bonnet parameter on the Strokes
$Q$-$U$ loops.
