The acousto optic tunable filter is restricted by the spectral range due to the limit of operating bandwidth of piezoelectric transducer. This article introduces a new way of improving the spectral range by improving the operating bandwidth of acousto optic tunable filter after setting more transducers with various thickness on one sound surface.With this new method,the acousto optic tunable filter with full spectrum can be realized in theory.The experimental results show that the proposed acousto optic tunable filter with two transducers has an operating bandwidth of nearly 0.9 octave;its spectral range covers from 0.45 μm to 0.95 μm,diffraction efficiency is great than 70%,spectral resolution is less than 7 nm,and light aperture is 8 mm×8 mm.