Acousto-optic tunable filter (AOTF) is a new type of dispersion components. It is widely used in the field of hyper-spectral imaging, but diffraction angle changes along with wavelength when tuning, which will cause drift of images. To solve the problem caused by crystal dispersion of AOTF spectral camera, a prism is added to the emergent surface of the crystal. Through the analysis of crystal optical rotation influence on crystal outside diffraction angle, it is found that when the incident angle is very large, crystal optical rotation must be taken into consideration. According to the basic analysis above, the relationship among prism vertex angle, the prism material and prism deviation angle is analyzed. The results show that when the incident angle is 28°, dispersion residual deviation of 0.0007° is achieved by adding 10.1° prism. This implies that the dispersion of AOTF spectral camera can be eliminated by adding the prism of proper material and vertex angle.