Manganese dioxide is a typical electrode material for supercapacitor due to its high theoretical capacitance and good environmental compatibility. However, the development of MnO₂ as electrode is limited by inferior conductivity, sluggish ionic transfer kinetics and poor cycling stability. Herein, we present a structure distortion strategy via Ni doping in MnO₂ to boost its Na⁺ storage performance. The as-obtained Ni-MnO₂ can deliver a high specific capacity of 379 F g^-1 at 1 A g^-1, excellent rate performance of 281 F g^-1 at 20 A g^-1, and a significantly enhanced cycling stability. In situ Raman results verify that Ni-MnO₂ with structure distortion can achieve a promising cycling life. Density functional theory results suggest that the structure distortion can efficiently modulate electron configuration by delocalizing electron. Furthermore, the Na⁺ diffusion energy barrier is remarkedly decreased in Ni-MnO₂, thus accelerating ionic transport kinetics. An asymmetric supercapacitor based on Ni-MnO₂ cathode exhibits a high energy density of 114.6 Wh kg^-1 at a power density of 3600 W kg^-1. This work verifies the efficiency of structure distortion strategy on the improvement of Na ion storage performance in MnO₂, which can be extended for the optimization of other electrode materials for energy storage.