The polymeric film embedded with polar bacteriorhodopsin (BR) molecules is isotropic in macroscopy since the BR molecules are randomly distributed. Upon excitation by a linearly polarized light, selective absorption of BR molecules with respect to the polarization orientation of the excitation light makes the nonuniformly distributed orientation of BR molecules, resulting in a macroscopic anisotropy. According to the two-state model of BR photocycle, the time-dependent orientation distribution of BR molecules in B state is obtained. The kinetic equations of the photoinduced anisotropy of the BR-film are derived. The kinetic curves of the photoinduced anisotropy at different intensities of excitation light are simulated, which are consistent with experimental results.