The natural vegetable dyes have the characteristics of non-toxicity, harmlessness andnon-pollution.Natural cellulose fiber fabrics dyed with natural vegetable dyes not only havemore added value but also have realized natural clothing.This is a good research on ecologicaland green textiles with the requirements of textile green consumerism of people in the newcentury. So the research of natural vegetable dyes benefits environment and human health.

The technology of supercritical carbon dioxide dyeing,known as "an innovative and green dyeing technology" with fast dyeing,good level dyeing,less cost and simple dyeing processes,has been concerned more and more. A flow-type dyeing apparatus was applied to toning dyeing of terylene fabric with disperse red 343 and disperse blue 366 in supercritical carbon dioxide using two processes(one bath dyeing process and two-bath dyeing process)at the temperature from 70 to 130 and pressures from 16 MPa to 24 MPa.

With thousands years, development of Chinese tranditional color culture, it shape the system which use the Five Colors as the nucleus of way to use colors . Using the Five Colors to classify the Vegetable Dyes is the most artistic characteristics of Chinese classifications.

Deficient water resources and serious pollution make it necessary to reuse wastewater. Textile industry is one of the industries that consume a large amount of water and generate tremendous pollutants. It is reported that usually the renewal percentage of polluted water is only less than 10%. The dyeing wastewater is the main pollution resource from textile industry, which not only takes a high volume but also contains large amount of contaminations.

A dye can generally be described as a colored substance that has an affinity to the substrate to which it is being applied. The dye is generally applied in an aqueous solution , and may require a mordant to improve the fastness of the dye on the fiber.

Both dyes and pigments appear to be colored because they absorb some wavelengths of light preferentially. In contrast with a dye, a pigment generally is insoluble, and has no affinity for the substrate. Some dyes can be precipitated with an inert salt to produce a lake pigment , and based on the salt used they could be aluminum lake, calcium lake or barium lake pigments.

Archaeological evidence shows that, particularly in India and the Middle East , dyeing has been carried out for over 5000 years. The dyes were obtained from animal , vegetable or mineral origin, with no or very little processing. By far the greatest source of dyes has been from the plant kingdom , notably roots , berries , bark , leaves and wood , but only a few have ever been used on a commercial scale.