The invention provides a device and method for measuring an integrated optical waveguide polarization extinction ratio. The device comprises a low-polarization-degree broad-spectrum light source, a polarization splitting white light interferometer and a signal detecting and processing system. The polarization splitting white light interferometer comprises a polarization beam splitter, a reference arm, a movable arm and a polarization beam combiner. The optical fiber polarization beam splitter is used for separating two orthogonally polarized light beams, all polarization maintaining pieces of the polarization splitting white light interferometer are reasonably connected, the problems of repeated coupling and multipoint mutual coupling occurring after a framing interferometer structure interferes beam combination are solved, the polarization extinction ratio characteristic points of integrated optical waveguides are accurately located and calculated in a quantified mode, and influence of light source power fluctuation on a measurement result is eliminated.