High‐entropy oxides (HEOs), known for their excellent thermodynamic stability due to their high‐entropy effect. In this study, high‐entropy (NixAlCoCrMn)3O4 oxides of spinel structure were synthesized by sol‐gel method. This HEO has a self‐reconfiguration properties in the reaction, and its internal Ni and Co ions exsolve to form a uniformly dispersed NiCot alloy on the surface. The increase of Ni content promotes the exsolution of Ni and Co ions from the interior of the spinel. The high‐entropy with a large number of oxygen vacancies not only possesses a stable structure to limit the migration of NiCo alloys, but also enhances the hydrogen overflow. In the CO methanation reaction, it has 99% CO conversion with 87% methane selectivity within 400 oC, and it is stable in the long‐term test. This work provides a new idea for exploring the use of high‐entropy materials to improve thermal catalytic activity and stability.