A Feynman diagram theory for acousto-optic (AO) interactions is established, which provides a general method to calculate the scattering amplitudes and intensities for both single-frequency and multifrequcncy AO interactions. The method is based on counting the number of allowable Feynman diagrams. The following important assertion has been proved rigorously in this paper. The ratios of the numbers of Feynman diagrams allowable in various B ragg diffractions (isotropie, nondegeneratc birefringent, and degenerate birefringent) to that in Raman-Nath diffraction are independent of the number of different acoustic frequencies, being a function only of the order of the Feynman diagram and the diffraction order of the final state. General expressions for these ratios arc obtained. Based on this, complete perturbation solutions for the scattering amplitudes and intensities are obtained for any kind of AO interactions, any number of acoustic frcquencies, and any final state. This theory gives all results obtain A Feynman diagram theory for acousto-optic (AO) interactions is established, which provides a general method to calculate the scattering amplitudes and intensities for both single-frequency and multifrequncy an AO interactions. The method is based on counting the number of allowable Feynman diagrams. The following important assertion has been demonstrated rigorously in this paper. The ratios of the numbers of Feynman diagrams allowable in various Bragg diffractions (isotropie, nondegeneratc birefringent, and degenerate birefringent) to that in Raman-Nath diffraction are independent of the number of different acoustic frequencies, being a function only of the order of the Feynman diagram and the diffraction order of the final state. General expressions for these ratios arc obtained. Based on this, complete perturbation solutions for the scattering amplitudes and intensities are obtained for any kind of AO interactions, any number of acoustic frcquencies, and any final state. This theory gives all results obtain