In this paper, MnO₂/MXene–Ti₃C₂ composites with different molar ratios were successfully prepared by a one-step hydro-thermal method, and the optimum proportion was confirmed by XRD and SEM comparative analysis. The optimum proportion of MnO₂/MXene–Ti₃C₂ composites and MnO₂ was used as a cathode material for magnesium batteries to carry out the electrochemical performance test. The results showed that the charge–discharge capacity of the MnO₂/MXene–Ti₃C₂ composite was up to 105 mA h g⁻¹, much higher than that of MnO₂ (64 mA h g⁻¹), and meanwhile it had good rate performance. At the same time, this also opened up the application of MXene–Ti₃C₂, a new two-dimensional material, in the field of battery electrode materials.