Acousto-optic tunable filters (AOTF) are widely used in hyperspectral imaging systems as filtering devices. It has the advantages of stable structure, fast tuning and high portability. This paper report the tuning of AOTF by controlling the incident angle and obtains the relationship between the angle of the incident light and the wavelength of the diffracted light. The characteristic of angular spectrum selection of AOTF was demonstrated experimentally. A spatial filter system of acousto-optic method is designed by combining AOTF and Fourier lens. The functions which enhance imaging contrast of the system are completed by a single AOTF device. Using this system the edge enhanced image of resolution target was acquired. Different from using a diaphragm for spatial filtering, this filtering method based on acousto-optic effects is continuously adjustable, real-time and stable, and provides a new idea for enhancing the contrast of optical images. © 2021 COPYRIGHT SPIE.