The design and synthesis of oxygen evolution reaction (OER) electrocatalysts that operate efficiently and stably under acidic conditions are important for the preparation of green hydrogen energy. The low intrinsic catalytic activity and poor acid resistance of commercial RuO₂ limit its further development, and the construction of heterointerface structures is the most promising strategy to break through the intrinsic activity limitation of electrocatalysts. Herein, we synthesized spherical and oxygen vacancy-rich heterointerface MnO₂/RuO₂ using morphology control, which promoted the kinetics of the oxygen evolution reaction with the interaction between oxygen vacancies and the oxide heterointerface. MnO₂/RuO₂ was reported to be an acidic OER catalyst with excellent performance and stability, requiring only an ultra-low overpotential of 181 mV in 0.5 M H₂SO₄ to achieve a current density of 10 mA cm⁻². The catalyst activity remained essentially unchanged in a 140 h stability test with an ultra-high mass activity (858.9 A g⁻¹@ 1.5 V), which was far superior to commercial RuO₂ and most previously reported noble metal-based acidic OER catalysts. The experimental results showed that the effect of more oxygen vacancies and the heterointerfaces of manganese ruthenium oxides broke the intrinsic activity limitation, provided more active sites for the OER, accelerated reaction kinetics, and improved the stability of the catalyst. The excellent performance of the catalyst suggests that MnO₂/RuO₂ provides a new idea for the design and study of heterointerfaces in metal oxide nanomaterials.