The invention discloses thermal transfer printing ink and a preparation method thereof. The thermal transfer printing ink is prepared from the following components in parts by weight: 15 to 25 parts of heat transfer printing disperse dye, 1 to 4 parts of rosin polyether sulfonate, 0.1 to 0.5 part of graphene, 10 to 15 parts of betaine, 1 to 3 parts of rose extract, 15 to 20 parts of hyperbranched polyglycerol, 1 to 2 parts of water-soluble chitosan, 0.1 to 0.5 part of preservative, 0.3 to 0.6 part of macromolecular surfactant, 30 to 40 parts of water and 10 to 20 parts of alcohol solvent. The invention also discloses a preparation method of the thermal transfer printing ink. The thermal transfer printing ink is high in fixation rate, antibacterial, good in storage stability, high in printing fluency, excellent in color reducibility, remarkable in waterproof, scratch-resistant and sun-proof effects, safe and environment-friendly to use and not liable to age, and white smoke and odor cannot be generated during color development of the ink.