P2-type transition metal layered oxides (TMOs) have gathered significant interest by virtue of their low-cost and excellent cycling stability. However, the extensive practical application of TMOs is constrained by inherent factors, such as inferior rate performance and deficient interfacial stability. Herein, the gradient Ta-doped Na0.78(Ni0.33Mn0.67)1-xTaxO2 (NMT) cathode material was synthesized via a one-step solid-state reaction method to overcome these obstacles. The Ta modification augments the Ni2+/Ni3+ redox couple activity, in accordance with the principle of charge conservation, thus bolstering the reversible capacity of the material. Furthermore, the gradient Ta-doping not only preserves the stability of the bulk phase of TMOs but also serves as a potent suppression against the emergence of deleterious interfacial side reactions. As a result, the NMT cathode delivers an improving initial discharge specific capacity of 105 mAh g−1 at 0.1 C and sustains an excellent capacity retention of 91.4 % after 500 cycles at 5 C within the voltage range of 2.0–4.0 V. Benefiting from the robust Ta–O bond, the highly reversible structure evolution of the gradient Ta-doped material during the Na+ extraction/insertion process is clearly elucidated through in-situ XRD. This research provides a straightforward and efficacious approach to elevate the electrochemical performance of TMOs for sodium-ion batteries (SIBs) in the future.