In this work , using the Gaussian Process , we explore the potentiality of future gravitational wave ( GW ) measurement to probe cosmic opacity through comparing its opacity-free luminosity distance ( LD ) with the opacity-dependent one from type Ia supernovae ( SNIa ) .
GW data points are simulated from the third generation Einstein Telescope , and SNIa data are taken from the Joint Light Analysis ( JLA ) or Pantheon compilation .
The advantages of using Gaussian Process are that one may match SNIa data with GW data at the same redshift and use all available data to probe cosmic opacity .
We obtain that the error bar of the constraint on cosmic opacity can be reduced to \sigma _ { \epsilon } \sim 0.011 and 0.006 at 1 \sigma confidence level ( CL ) for JLA and Pantheon respectively in a cosmological-independent way .
Thus , the future GW measurements can give competitive results on the cosmic opacity test .
Furthermore , we propose a method to probe the spatial homogeneity of the cosmic transparency through comparing the reconstructed LD from the mock GW with the reconstructed one from SNIa data in a flat \Lambda CDM with the Gaussian Process .
The result shows that a transparent universe is favored at 1 \sigma CL , although the best-fit value of cosmic opacity is redshift-dependent .

\mathbf { Keywords: } Cosmic opacity , gravitation wave