The contribution of graphene oxide (GO) on photocatalytic effects of CuxO on plasmonic Au is investigated. It is found that the H2 evolution rate from pure water is enhanced 1.4 fold using the visible-active CuxO/GO photocatalyst, as compared with CuxO without GO. In addition, the intensity of photoluminescence of CuxO/GO can be enhanced as much as 2.85 fold as compared with CuxO without GO. The enhancement is due to the negative fixed charge in GO, which can passivate the surface of CuxO and suppress recombination of minority electrons at the surface. The results from optical characterization in this study can help to prove the proposed mechanism of passivation.