A method for preparing a reference electrode and a lithium ion battery with a reference electrode. In some embodiments, a method includes the following steps: welding a reference electrode substrate to a lower portion of a current collector metal sheet with a tab-film; melting metal lithium into a liquid state; immersing a lower portion of the reference electrode substrate welded with the current collector metal sheet into the liquid lithium; coating a lower portion of the tab-film with a layer of separator to obtain a reference electrode with a separator coating; inserting the reference electrode between a separator of a core of a lithium ion battery and an anode piece; and packaging in plastic the lithium ion battery implanted with the reference electrode to obtain the lithium ion battery with the reference electrode.