The researchers generally studied one channel all fiber modulator. In order to develop the great capability of optical fiber, the multiple channel all fiber acousto optical modulator should be concerned. The multiple channel all fiber acousto optical modulator is studied theoretically. The perturbed coupled mode theory is used to discuss the solutions of coupled mode equations for optical fiber when there are multiple parts being perturbed, and the multiple channel modulation is analyzed. The results can be used as a basis of experimental research.