Based on the multi-frequencies mode of Acousto-Optical Tunable Filter (AOTF), the technique of spectral programmability for imaging spectrometer has been proposed. The principles of this technique were presented, and the test results of spectral programmability were introduced, including controls on the filtered wavelength, spectral resolution and passband shape of AOTF via software. Then a prototype system of spectrally programmable imaging spectrometer was established. Primary imaging experiments was carried out to validate the engineering feasibility and technical advantages of the technique. A novel method was provided for increasing the efficiency and flexibility of imaging spectrometers.