Hydrophobic surfaces of cellulose acetate(CA) fabrics were modified to give more hydrophilicity via $UV/O_3$ irradiation. The surface change of chemical structure and composition were investigated by ATR and ESCA analysis. The UV irradiation treatment caused ester linkage of the acetyl groups to break down and new photo-oxidated products were generated as indicated in subtracted ATR spectra and $O_{1s}/C_{1s}$. Also degree of acetylation of the irradiated CA fabrics decreased with increasing UV energy. It was found that the dyeability of the modified acetate remarkably improved particularly toward cationic and reactive dyes, while disperse dyeability of the modified fabrics decreased noticeably at the irradiated surface. Effect of change in various dyeing conditions including dye concentration, dyeing time and temperature on cationic dyeing were assessed to find optimal dyeing condition. The colorfastness of the acetate fabrics to laundering and rubbing was good enough in spite of surface coloration of the acetate fabrics inevitable in the UV treatment and subsequent dyeing.