Structural design and modification are effective approaches to regulate the physicochemical properties of TiO2, which play an important role in achieving advanced materials. Herein, a plasma‐assisted method is reported to synthesize a surface‐defect‐rich and deep‐cation‐site‐rich S doped rutile TiO2 (R‐TiO2–x‐S) as an advanced anode for the Na ion battery. An amorphous shell (≈3 nm) is induced by the Ar/H2 plasma, which brings about the subsequent high S doping concentration (≈4.68 at%) and deep doping depth. Experimental results and density functional theory calculations demonstrate greatly facilitated ion diffusion, improved electronic conductivity, and an increased mobility rate of holes for R‐TiO2−x‐S, which result in superior rate capability (264.8 and 128.5 mAh g−1 at 50 and 10 000 mA g−1, respectively) and excellent cycling stability (almost 100% retention over 6500 cycles). Such improvements signify that plasma treatment offers an innovative and general approach toward designing advanced battery materials. Surface amorphous TiO2 with a high content of cation‐site‐doped S is achieved with the assistance of plasma. Those features give rise to greatly improved intrinsic electronic conductivity and enhanced sodium‐ion diffusion of TiO2, leading to superior sodium‐storage performance. This strategy opens a new avenue to design advanced materials for energy‐storage systems.