The invention discloses an all-solid-state lithium ion battery and a preparation method thereof. The all-solid-state lithium ion battery is prepared by an ink-jet printing technology; different components are dissolved into a solvent to prepare slurry; the slurry is put into different ink boxes; designing is carried out by computer program; electrodes and electrolyte are longitudinally printed in a stepwise gradient manner; the electrolyte longitudinally changes in electrode plates in a gradient manner; the interface impedance of an electrode active material/electrolyte can be reduced by the gradient structure distribution of the electrolyte in the electrode plates; deep conduction of lithium ions is facilitated; the capacity property of the active material is put into the greatest play; and other parts, except for a current collector, of the all-solid-state lithium ion battery structure prepared by ink-jet printing form an overall lamination structure. Various components in the lamination structure are in tight contact and regular arrangement, so that the interface impedance is much lower than that of the all-solid-state lithium ion battery which is prepared in a mechanical superposition manner; and the ink-jet printing mode is convenient, fast and suitable for large-scale production.