  In this work, using the Gaussian process, we explore the potentiality of
future gravitational wave (GW) measurements to probe cosmic opacity at high
redshifts through comparing its opacity-free luminosity distance (LD) with the
opacity-dependent one from the combination of Type Ia supernovae (SNIa) and
gamma-ray bursts (GRBs). The GW data, SNIa and GRB data are simulated from the
measurements of the future Einstein Telescope, the actual Pantheon compilation
and the latest observation of GRBs compiled by L. Amati {\it et al},
respectively. A nonparametric method is proposed to probe the spatial
homogeneity of cosmic transparency at high redshift by comparing the LD
reconstructed from the GW data with
  that reconstructed from the Pantheon and GRB data. In addition, the cosmic
opacity is tested by using the parametrization for the optical depth, and the
results show that the constraints on cosmic opacity are more stringent than the
previous ones. It shows that the future GW measurements may be used as an
important tool to probe the cosmic opacity in the high redshift region.
