The present invention provides an optical waveguide photosensitive resin composition containing a resin component and a photoacid generator, wherein the photoacid generator has a characteristic property (x) such that an absorption limit (O—O transition energy) calculated based on the shape of an ultraviolet spectrum obtained by spectrometrically analyzing a 0.1 wt % propylene carbonate solution of the photoacid generator by means of an ultraviolet/visible spectrophotometer is 3.5 to 4.1 eV. Where an optical waveguide core layer is formed by using the inventive optical waveguide photosensitive resin composition, for example, the optical waveguide core layer has a lower loss, and is excellent in patternability and reflow resistance.