Hydrophilic UV-curable PU oligomers (UV-PU) were prepared by mixing either the toluene diisocyanates (TDI) with polyethylene glycol-1000, or the isophorone diisocyanate (IPDI) with polypropylene glycol-1000 and dimethylol propanic acid (DMPA), to produce the desired carboxylic acid bearing or non-ionic PU oligmer (NCO-PU), separately. The 2-hydroxyethyl methacrylate (HEMA) was then added into the NCO-PU oligomer to form acrylate-terminated (UV-curable) PU oligomer (UV-PU). The reactive diluents, such as 1,6-hexanediol diacrylate (HDDA), trimethylolpropane tricarylate (TMPTA) and others were used to adjust the viscosity of UV-PU and to control the concentration of acrylic group. The hydrophilic UV-curable PU system was formulated and applied on PET micro-fiber and then cured by an UV-radiation at ambient temperature. The physical, thermal, and mechanical properties, in particular, the hydrophilic properties of UV-curable PU treated PET micro-fibers will be discussed.