The charge and discharge performance of 18650 Li-ion battery was studied in a magnetic field environment, and it was found that the charge and discharge capacities of the battery increased with the increase of magnetic field strength at the same charge and discharge rates. At different charge and discharge rates, the higher the multiplier, the more obvious the battery capacity is affected by the magnetic field. Under the scanning electron microscope, it was found that the cracking phenomena of the cathode and anode materials of the battery were obvious without application of magnetic field environment. While the magnetic field was applied, the cracking phenomenon diminished. The magnetic field environment affects the direction of the movement of materials inside the battery, which makes the lithium ions evenly distributed and suppresses the cracking phenomena of the cathode and anode materials, thus reducing the capacity decay rate of lithium-ion battery and obtaining a larger capacity gain.