The invention discloses a cylindrical-structure lithium ion battery and a preparation method thereof. The cylindrical-structure lithium ion battery comprises a cylindrical cell externally coated with a packaging film; a positive tab and a negative tab of the cell penetrate through the packaging film; the positive tab and the negative tab are arranged on the side wall of the cell and parallel with the axis of the cell and has the same orientation with the cell axis. Adoption of the cylindrical-structure lithium ion battery and the preparation method thereof abandons steel shell structure batteries with high cost, heavy weight and poor safety and soft-packaged batteries with a low energy ratio; the cylindrical-structure lithium ion battery and the preparation method thereof have the advantages of higher safety and energy ratio and longer service life.