Rechargeable magnesium batteries (RMBs) are considered as one of the most promising candidates for next‐generation batteries. However, the popularization of RMBs is seriously plagued due to the lack of suitable non‐nucleophilic electrolytes and the passivation of Mg anode. Herein, a novel non‐nucleophilic electrolyte is developed by introducing (s)‐1‐methoxy‐2‐propylamine (M4) into themagnesium aluminum chloride complex (MACC)‐like electrolyte. The as‐synthesizes Mg(AlCl4)2‐IL‐DME‐M4 electrolyte enables robust reversible cycling of Mg plating/stripping with low overpotential, high anodic stability, and ionic conductivity (8.56 mS cm−1). These features should be mainly attributed to the in situ formation of an MgF2 containing Mg2+‐conducting interphase, which dramatically suppresses the passivation and parasitic reaction of Mg anode with electrolyte. Remarkably, the Mg/S batteries assemble with as‐synthesize electrolyte and a new type MoS2@CMK/S cathode deliver unprecedented electrochemical performance. Specifically, the Mg/S battery exhibited the highest reversible capacity up to 1210 mAh g−1 at 0.1 C, excellent rate capability and satisfactory long‐term cycling stability with a reversible capacity of 370 mAh g−1 (coulombic efficiency of ≈100%) at 1.0 C for 600 cycles. The study findings provide a novel strategy and inspiration for designing efficient non‐nucleophilic Mg electrolyte and suitable sulfur‐host materials for practical Mg/S battery applications. This work is developed an advanced non‐nucleophilic Mg(AlCl4)2‐IL‐DME‐M4 electrolyte and suitable MoS2@CMK/S cathode. Due to the in situ formation of advantageous MgF2 containing SEI at Mg/electrolyte interface, the assembled Mg/S batteries are delivered the highest capacity of 1210 mAh g‐1 at 0.1 C and exhibited excellent long‐term cycling stability with reversible capacity of 370 mAh g‐1 at 1.0 C for 600 cycles.