Abstract: The size of anode materials has an essential effect on the performance of lithium-ion batteries. The grinding time was designed to prepare different sizes of natural molybdenite, and the relationship between the size and the electrochemical performance of lithium-ion batteries was explored. The average sizes of the samples abraded for 30 (M30), 60 (M60), and 90 min (M90) were 19.45, 13.14, and 11.23 μm, respectively. XRD and SEM show that the smaller the particle size, the smaller the grain size, and the more serious the edge crushing is. Electrochemical performance tests showed that the first cycle capacities of the three groups were 851, 797, and 649 mAh·g^-1, respectively, and the capacity retention rates after 100 cycles were 30%, 38%, and 85%, respectively. M90 had the maximum lithium-ion diffusion coefficient of 3.29×10^-10, and the pseudocapacitance was the main contribution to the capacity calculated at different CV scanning rates of 0.1~0.8 mV·s^-1, which could realize rapid electron and ion shuttle. The smaller the size of natural molybdenite, the smaller the first cycle capacity, but better cycle and rate performance and faster reaction kinetics, and similar to the natural molybdenite layered lithium storage model were proposed to clarify the relationship between the size of natural molybdenite and the performance of the lithium-ion battery.