A differential-phase polarization-sensitive optical coherence tomography system includes a polarized heterodyne interferometer for generating a reference beam to be reflected by a movable mirror unit, and a signal beam to be reflected by an imaging plane in a specimen. The interferometer further generates a first electrical signal output corresponding to first linear polarized waves of the reference and signal beams, and a second electrical signal output corresponding to second linear polarized waves of the reference and signal beams. A differential amplifier receives the first and second electrical signal outputs, and generates a differential signal output therefrom. A data acquisition unit is used to measure amplitudes of the first and second electrical signal outputs and the differential signal output. A computing unit computes the amplitudes measured by the data acquisition unit to determine a reflectivity, a phase retardation, and a fast axis angle of the imaging plane in the specimen.