Abstract In this paper the theoretical and experimental studies on the properties of phase conjugate (PC) wave and the gratings formed as a result of degenerate four-wave mixing (DFWM) interference field of Ar+ laser in bacteriorhodopsin-polyvinyl alcohol (BR-PVA) solid film are reported. The diffraction efficiency temporary response and saturation property of the PC wave are described by useing a simplified double state model and the method of rate equation combined with a diffraction theory of holograph grating. The mechanism of forming grating in the film and the dependence of the properties mentioned above on polarization states, intensities are analysed. The time of arriving at the sample of three input beams and initial concentration of grating formed in the film are discussed. The theoretical results are in good agreement with the experimental observations.