Layered transition metal oxides have drawn much attention as a promising candidate cathode material for sodium‐ion batteries. However, their performance degradation originating from strains and lattice phase transitions remains a critical challenge. Herein, a high‐concentration Zn‐substituted NaxMnO2 cathode with strongly suppressed P2–O2 transition is investigated, which exhibits a volume change as low as 1.0% in the charge/discharge process. Such ultralow strain characteristics ensure a stable host for sodium ion storage, which significantly improves the cycling stability and rate capability of the cathode material. Also, the strong coupling between the highly reversible capacity and the doping content of Zn in NaxMnO2 is investigated. It is suggested that a reversible anionic redox reaction can be effectively triggered by Zn ions and is also highly dependent on the Zn content. Such an ion doping strategy could shed light on the design and construction of stable and high‐capacity sodium ion host. A high‐concentration Zn‐substituted P2‐type is found to exhibit ultralow strain characteristics as a high‐performance sodium‐ion battery cathode. In the sodiation/desodiation process, this P2‐Na2/3Zn0.25Mn0.75O2 exhibits a near zero strain extending along the c‐direction (0.8%) and a small change in volume (1.0%), which significantly improves the cycling stability and rate capability of the cathode material.