Chinese purple BaCuSi₂O₆ is a kind of the ancient Chinese artificial pigment named barium copper silicate, representing a unique civilization achievement and a high level of science and technology in ancient China. Hydrothermal synthesis is a relatively new method in recent years to dissolve substances insoluble or sparingly insoluble under atmospheric conditions by means of high temperature and pressure water vapor, recrystallize them for inorganic synthesis and material treatment. Based on previous studies, this paper adopted the hydrothermal synthesis method, selected BaCl₂·2H₂O, CuO, Na₂SiO₃·9H₂O as raw materials, and weighed them according to the stoichiometric ratio of the target products, the influence factors such as the pH environment of the solution, the synthesis temperature and the holding time of the solution were adjusted to prepare high-purity Chinese purple. XRD characterized the phase and purity of the product. The experimental results showed that Chinese purple with higher purity could be produced at 10 ≤ pH ≤ 12, and the purity of Chinese purple at 160 ℃ was higher than that at 180 ℃, and the purity of Chinese purple increased with the extension of the hydrothermal time. It is concluded that the optimal preparation condition for the hydrothermal preparation of Chinese purple is that pH 12, the temperature reaches 160 ℃, and the holding time lasts for 48 h. In addition, the discovery of intermediates BaSi₂O₅ and Ba₄Si₆O₁₆ demonstrates that Ba and Si first combined in different forms through O during the growth of barium copper silicate crystals, and Cu finally participated in the construction of barium copper silicate crystals. To sum up, this study provides a new method for the synthesis of pure Chinese purple, which can be used to protect and restore cultural relics. It can also provide a basis and clue for the synthesis mechanism of Chinese purple, which has a considerable role in promoting the research on the history of ancient Chinese science and technology.