A method for making a thin film lithium ion battery is provided. A cathode material layer and an anode material layer are provided. A carbon nanotube array is applied to a surface of the cathode material layer and pressed to form a first carbon nanotube layer on the surface of the cathode material layer to obtain a cathode electrode. A second carbon nanotube layer is formed on a surface of the anode material layer to obtain an anode electrode. A solid electrolyte layer is applied between the cathode electrode and the anode electrode to form a battery cell. At least one battery cell is then encapsulated in an external encapsulating shell.