Polyester fabrics were irradiated by UV produced by the low pressure mercury lamp. UV irradiation broke a C-H bond of PET fiber and caused the carbonyl groups on the fiber surfaces. Surface modification of PET fibers were accelerated by pretreatment with methanol, ethanol and acetone. The irradiated PET was dyed with basic dyes having cationic groups. The dye uptakes were proportional to irradiation times, and in inversely proportional to irradiation distances. The tensile strengths of PET fabrics decreased by UV irradiation. Washing fastness of PET dyeings were good, about 4-5 grade,andlightfastnesswerepoor, about l grade. ,