Published 9 October 2012 In conventional polarization-sensitive optical coherence tomography (PS-OCT), phase retardation is obtained by the amplitude of P and S polarization only, and the fast axis angle is obtained by the phase difference in P and S polarizations via Hilbert transformation. In this paper, we proposed a modified PS-OCT setup in which the phase retardation and fast axis angle are simply expressed as the function of the amplitude of P and S polarization and their differential signal. Due to the common-path feature between the two channels of P and S polarization, the fluctuation in the measurement of phase retardation and fast axis angle caused by excess noise and phase noise from the laser source can be reduced by the differential signal of P and S polarization via a modified balance detector. Thus, the signal of phase retardation and fast angle axis in the deep layer of a porcine sample can be improved.