Cascaded diam-etched fiber was studied to realize the dynamic manipulation of dual-wavelength filter.Utilizing the coupled-mode theory and segmented transfer matrix method,the theoretical derivation and simulation calculation were carried out.A new type of tunable dual-wavelength filter was studied based on cascaded Acousto-Optic Gratings(AOGs) in diam-etched fiber.The side lobe suppression effect of diam-etched AOGs in the transmission spectra was analyzed.The results show that optical fiber etching method can effectively suppress the side lobe effect,the side lobe ratio can be decreased from 0.265 to 0.031;The dual-wavelength filter works symmetrically and efficiently with tunable frequency spacing by adjusting the fiber length.When the fiber length increases,left resonant wavelength peak decreases and right resonant wavelength peak increases.The wavelength of the dual wavelength filter tunable adjusted by the frequency of the acoustic signal and the number of segments of the fibers,the dual-wavelength increases with the acoustic wave,and approximately linearly between 270 μm to 282 μm,the wavelength shift enlarges with the number of fiber segments increasing.