The design and preparation of anode materials with structural stability, fast ion transmission, and low open-circuit voltage are critical to the development of magnesium ion batteries (MIBs). The feasibility of the unique phase Haeckelite MoS2 (Hae-MoS2) monolayer with Haeckelite structure as a potential anode material for MIBs was investigated using density functional theory (DFT) calculations. The Hae-MoS2 monolayer exhibits excellent structural stability and semimetallic characteristics with a Dirac cone located at the Gamma point of band structure. Mg ion is easily adsorbed on the Hae-MoS2 monolayer surface with an adsorption energy of -2.06 eV and can diffuse rapidly with a low diffusion energy barrier (0.3 eV), indicating excellent charge and discharge rates. Most importantly, the Hae-MoS2 monolayer exhibits a suitable open-circuit voltage, which falls within the desired voltage range and ensures the safety of battery performance. These exceptional properties indicate that the Hae-MoS2 monolayer can be proposed as a candidate for anode material for MIBs.