  We investigate the shadows and photon spheres of the four-dimensional
Gauss-Bonnet black hole with the static and infalling spherical accretions. We
show that for both cases, the shadow and photon sphere are always present. The
radii of the shadow and photon sphere are independent of the profiles of
accretion for a fixed Gauss-Bonnet constant, implying that the shadow is a
signature of the spacetime geometry and it is hardly influenced by accretion in
this case. Because of the Doppler effect, the shadow of the infalling accretion
is found to be darker than that of the static one. We also investigate the
effect of the Gauss-Bonnet constant on the shadow and photon sphere, and find
that the larger the Gauss-Bonnet constant is, the smaller the radii of the
shadow and photon sphere will be. In particular, the observed specific
intensity increases with the increasing of the Gauss-Bonnet constant.
