天然色素安全系数高、可生物降解、对棉纤维具有较好的直接性，适合作为专用染料用于超临界CO2棉染技术。但天然色素在超临界CO2中溶解度偏低、与棉纤维结合力较弱导致其在超临界CO2中染色棉纤维时存在色深低、水洗摩擦牢度差的问题，无法在超临界CO2棉染技术中进行实际应用。本申请提出将促溶基团（烷基、氰基、硝基、酯基和卤素基团）和能与棉纤维反应的基团（羟甲基、羧基）引入天然色素中合成天然结构染料。通过促溶基团提高天然结构染料在超临界CO2中的溶解度，从而提高染后棉纤维的色深；通过能与棉纤维反应的基团提高天然结构染料与棉纤维的结合力，从而提高染后棉纤维的水洗摩擦牢度。阐明促溶基团和能与棉纤维反应的基团对天然结构染料在超临界CO2中染色性能的影响规律，为发展超临界CO2染色、获得性能优良的超临界CO2棉用染料提供新途径和理论指导。

Natural pigment is of high security, biodegradable and has good substantivity with cotton fiber, therefore it is suitable for cotton supercritical carbon dioxide (SC-CO2) dyeing technology. But the low supercritical CO2 solubilities and less firm cotton-bindings of natural pigments cause the problem of the low color depths and poor fastnesses (washing & rubbing) of cotton fiber dyed in supercritical CO2 technology, which results in the supercritical CO2 dyeing technology to be unavailable to the commercial application. This application proposes an idea for introducing promoting soluble groups (alkyl, cyan, nitro, ester and halogen groups) and functional groups capable of reacting with cotton (hydroxymethyl, carboxyl groups) to natural pigments to synthesize natural structure dyes. By promoting soluble groups, the solubilities of natural structure dyes in SC-CO2 will be enhanced, and further the color depths of cotton dyed by natural structure dyes will be improved; by functional groups capable of reacting with cotton, the bindings between dyes and cotton fiber will be strengthened, and further the fastnesses (washing & rubbing) of cotton dyed by natural structure dyes will be improved. The effect of the promoting soluble groups and functional groups capable of reacting with cotton on the dyeing property of natural structure dyes will also be illuminated. By this way, supercritical CO2 dyeing technology will be developed, good performance of supercritical CO2 cotton dyes will be obtained, and a new method and theoretical guidance will be provided.