Copper element with low chemical activity is hard to be used as the major active site for oxygen evolution reaction (OER). To improve its OER performance, a specialized structural and chemical environments need be designed. In this work, the composite electrocatalyst of Agn@HEO were synthesized by a simple co-precipitation plus annealing methods. With the aid of the elemental Ag0 atom, part of Cu ions in high entropy oxide (HEO) phases were gradually transferred to the elemental Cu0 atoms and mixed with Ag0 atom for CuAg alloy. This transition evidently altered the chemical environments of Cu element. Thanks to the largest molar percentage of Cu0 atom, the designed Ag1@HEO specimen exhibited the fairly low experimental OER overpotential of 249 (308) mV at the current density of 10 (100) mA cm−2 with the small Tafel slope of 55.2 mV dec-1 and stable electrocatalytic activity. Based on the density functional theory simulation, the theoretical OER overpotential of Cu active site could be adjusted along with the ridges of “volcanic” in both atomic and ionic environments, and achieved the smallest value of 213 mV as the d band center of Cu0 atom had a suitable value near the “volcanic” peak. This design strategy would be adopted to provide an effective enhancement scheme for OER on Cu active site.