Abstract: The dyeing systems containing penetrant DP、sodium hydrosulphite、caustic soda and indigo dye were used to dye the cotton fabric by the use of Minitab software, 20 groups dyeing designed by central composite method were carried out, the fabrics were impregnated with dyeing solutions for 20s at 25oC, then padding to keep pick up at 60% and oxidized for 75s. The dye-uptake, the K / S value, the wet and the dry rubbing fastness and the tensile strength of the dyed fabrics were measured and the distribution of the dye in the yarn cross section were observed and analyzed. The results showed that the yarns were evenly dyed and all of dye uptake, K / S value, rubbing fastness and tensile strength were improved .The optimum dosage are: caustic soda 6.63g/L,sodium hyposulfite 5.65g/L,alkali penetrant DP 0.97g/L.

Key words: penetrant, central composite design, indigo dye, cotton fabric, dyeing