The optical and physical properties of alkyl-substituted anthraquinoid dyes were investigated in terms of dyeing of pure polypropylene fiber. The length of alkyl substituents of the dyes did not affect the molar extinction coefficient and maximum absorption wavelength of them. The use of a double-tailed cationic surfactant, didodecyldimethylammonium bromide(DDDMAB), could make the hydrophobic dyes dispersed in water effectively. As the amount of DDDMAB increased, the average particle size of dye dispersion decreased. Maximum color strength of the fabrics was shown in the case that 1.5 molar ratio of DDDMAB was used. As for the fastness properties, commercially acceptable result was obtained in general.