Designing efficient and stable electrocatalysts for the hydrogen and oxygen evolution reactions (HER and OER) is crucial for green hydrogen production via the water‐splitting system. The bifunctional electrocatalyst offers a promising strategy due to the simplified preparation process and reduced expenses. However, the single‐component bifunctional catalysts often struggle to match the redox potential of water and to achieve proper adsorption/desorption of Gibbs free energy for both H and O intermediates simultaneously. Herein, through precisely controlling the topological transformation path of the RuNiOx precursor, we successfully prepared high‐performance RuNi/Ni and Ru/NiO heterostructure electrocatalysts for the HER and OER, respectively. The energy level matching between the fabricated electrocatalyst and water oxidation/reduction potential confirms the feasibility of HER and OER. The synergistic effect between the active sites ensures rapid, intermediate adsorption/desorption kinetics. As a result, the assembled alkaline overall water splitting setup achieves a current density of 1 A cm‐2 at 2 V and maintains stable operation at 100 mA cm‐2 for 100 hours.