A process for synthesizing VK2 from solanesol includes such steps as purifying solaneol, dissolving 2-methyl-1,4-naphthylquinone in methanol, adding cyclopentadiee and Lewis acid or protonic acid, reaction to obtain the compound A (1,4,4a,9a-tetrahydro-9a alpha-methyl-1 alpha, 4 alpha-methyl bridge anthraquinone), dissolving solaneol in hexane, adding PBr3, extracting in petroether to obtain solanylbromine, dissolving it in tetrahydrofuran, dripping in said compound A, adding solvanylbromine, reaction to obtain compound B, dissolving it in toluene, and reflux to obtain VK2.