Based on the analysis of the design theories[1,2] for non-collinear acoustooptic tunable filter (AOTF), this paper analysed and accurately calculated the angular dependence between the acoustic polar angle θa and incident light polar angle θi for TeO2. θa-θi curve satisfied the parallel- tangents momentum- matching condition for non- collinear AOTF with a maximum angular aperture is obtained. The resulted curve obviously improved the θa-θi curve of Chang[2], and it provides a solid theoretical basis for the design of TeO2 AOTF.