The invention relates to a traditional Chinese medicine decoction additive for water-based ink and a preparation method thereof. The additive comprises the following Chinese herbal medicine components in percentage by mass: 10-30% of garlic, 10-30% of eucommia, 2-20% of lavender, 0-20% of cinnamon, 0-20% of gamboge, 0-20% of saponin, 0-20% of mint, 0-20% of Amomum cardamomum, 0-20% of aniseed, 2-20% of clove, 2-20% of thyme, 2-20% of pomegranate rind, 2-20% of orange peel, 2-10% of pepper and 2-10% of ginger. The method comprises the following steps: adding water, wherein the weight ratio of the traditional Chinese medicine components to the water is 1:10; and slightly boiling on a slow fire with a stainless steel lid covered for about two hours, removing filter residues by filtration with a copper screen of 300 meshes to obtain the filtrate as the Chinese herbal medicine decoction. When the Chinese herbal medicine decoction is added to the water-based ink in the mass percentage of 1-10, the ink gives out faint scent, has the functions of corrosion prevention, sterilization and borer resistance, and has moist looking and thick color.