New soluble photosensitive poly(amide-co-imide) containing p-phenylenediacryloyl moiety was synthesized and its photoreactivity was characterized by UV-Vis spectroscopic methods. The copolymer was synthesized from p-phenylenediacryloyl chloride, bis(3,4-dicarboxyliphenyl)hexafluoropropane dianhydride (6FDA) and two equivalents of 2,2'-bis(trifluoromethyl)benzidine (BTBz) followed by chemical imidization. From the refractive index measurement by prism coupling method, it was found that the refractive index could be varied precisely with respect to the exposure time. Fabrication of passive waveguide was attempted by the photo-modulation of refractive index. Straight waveguide was easily fabricated and the single mode near-field pattern was observed by using 1.55 and 1.3 mum near-IR light.