An all-fiber band-pass acousto-optic tunable filter is proposed. By introducing a mode converter into a cladding-etched single-mode fiber, the fundamental mode transmitted in the core originally is blocked and the cladding mode is coupled in the fiber core at the same time. The results indicate that the band-pass filter has a blue shift when acoustic frequency increases, and the resonant peak of the filter decreases with the increase of cladding radius, moreover, the increase of the acoustic power can also increase the resonance peak of the filter to some extent. Meanwhile, a band pass resonance peak with 3 dB bandwidth of 2.13 nm is obtained when the cladding radius is kept at 32.5 μm, and the acoustic power and frequency are fixed at 20 mW and 1.5 MHz respectively. The tunable wavelength of 85.18 nm can be achieved when the acoustic frequency is adjusted from 1.2 MHz to 1.5 MHz. The device has the potential to be applied into the fiber lasers with large gain bandwidth.