Owing to their highly tailorable electrochemical characteristics and exceptional reactivity, high-entropy materials represent the next generation of water splitting catalysts. In this work, rare earth elements (Ho, Dy, Pr and Gd) were equivalently co-doped into the A-site of Y₂Ru₂O₇, successfully resulting in a new-type high-entropy pyrochlore (Y_0.2Ho_0.2Dy_0.2Gd_0.2Pr_0.2)₂Ru₂O₇ (HE-YRO). The electrocatalyst presents an extremely low overpotential (η = 200 mV) and unobvious inactivation during stability testing at 10 mA cm⁻². More remarkably, at η = 270 mV, it shows an excellent inherent mass activity of 797.1 A g_Ru⁻¹. By analyses of related pyrochlore oxides, several characteristics are confirmed for the HE-YRO electrocatalyst, which endow it with the high oxygen-evolution reaction (OER) performance. First of all, compared to those in YRO, more low-valent Ru³⁺ species and oxygen vacancies are induced in the HE-YRO structure, which improves the performance. Secondly, inhibition of the grain coarsening is caused by the lattice distortion, which would lead to large surface areas for HE-YRO and then increase the OER active sites. Thirdly, the Ru 4d band is extended, which results in an enhancement of conductivity and a strengthened hybridization between O 2p and Ru 4d orbitals, and then improves the reaction kinetics of the OER. Therefore, the synergistic effect of the above factors that are induced by the equivalent multielement doping at the A-site results in the superior OER performance and chemical durability of the HE-YRO electrocatalyst for acid-water oxidation. This work not only presents a novel method for creating advanced materials for obtaining renewable and clean energy but also validates the efficacy of high-entropy design.