Crystal violet lactone (CVL), whose chemical name is 3,3-bis (4- dimethylaminophenyl) -6- dimethylaminophenyl peptide (3,3-bis -(4- dimethylaminophenyl) -6- dimethylaminophthalein), is a kind of heat-sensitive and pressure-sensitive dye with fast color development, high chroma and good oil solubility. At present, most of CVL needed in China depends on imports, so it is of great practical significance to study the synthesis method of CVL to promote the production of functional dyes in China. Generally, dyes are colored conjugated systems, which have the property of dyeing fibers or resins, while the conjugated systems of heat-sensitive and pressure-sensitive dyes are discontinuous and colorless, but have the property of reacting with color developers to produce colors. Under acidic conditions, the lactone ring of CVL is cracked to form a quinone-type large π-bond colored group, which emits a high concentration of bright blue-purple, with the maximum reflected light absorption at 609.8nm.