Abstract: The purpose of this paper is to investigate the effect of magnetic field-induced birefringence and dichroism on relaxation behavior of light transmissivity in ferrofluids film in term of the Xu’s oscillating magnetic dipole model and the Matsumoto’s birefringence relaxation theory.The specific expression of polarized light transmissivity about birefringence and dichroism is theoretically deduced and numerically simulated.The study has a certain significance on deeper understanding of the optical anisotropy and related application of ferrofluids.