To address the problem of rapid capacity decay of LiMn2O4 during the cycling process, Mn3O4 with different particle sizes and tap densities was prepared by manganese salt method, and used as a precursor to synthesize LiMn2O4 cathode material. The effects of Mn3O4 particle size and tap density on the electrochemical performance were investigated using X-ray diffraction, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests. The results indicate that increasing the particle size of the Mn3O4 precursor leads to a slight decrease in the initial discharge specific capacity, but significantly improves both cycling stability and rate performance. Compared with the material derived from 6 μm Mn3O4, the cathode material prepared from 10 μm Mn3O4 exhibits a 6.2% reduction in initial discharge capacity, while achieving an 8.0% increase in capacity retention after 300 cycles and a 25.2% improvement at 5 C. Moreover, when the tap density of Mn3O4 exceeds 2.5 g/cm3, the rate performance of the material deteriorates sharply. The LiMn2O4 sample prepared with a precursor particle size of 10 μm and tap density of 2.5 g/cm3 demonstrates the best overall electrochemical performance, delivering discharge specific capacities of 122.48, 111.9, and 78.42 mAh/g at 0.1, 1, and 5 C, respectively, along with a capacity retention of 90.3% after 300 cycles. This study clarifies the influence of precursor physical properties on the electrochemical properties of LiMn2O4, providing basis for the synthesis of high-performance LiMn2O4 materials.