Cu NPs (copper nanoparticles) were synthesized in situ on the surface of CuFe₂O₄ (cuprospinel). The enhancement of the separation efficiency of photogenerated e⁻/h⁺ and the catalytic quantum efficiency showed that the LSPR (local surface plasmon resonance) of Cu NPs facilitated the photocatalytic reaction activity of CuFe₂O₄. And due to the fact that CuFe₂O₄ was constructed with Cu–O in the tetrahedral site and Fe–O in the octahedral site, the results of DTG and Raman spectra after HER (hydrogen evolution reaction) displayed that the phase change of Fe–O in the octahedral site of CuFe₂O₄ took place during the HER process, and along with the peak of Fe²⁺ in XPS spectra after HER, which indicated that light activated Fe–O in the octahedral site was responsible for the photocatalytic process.