The rotating double-prism system allows the expansion of the imaging field of view and increase of apex angle of prisms through beam control, therefore increasing the magnification of the field of view but aggravating imaging distortion. This paper proposes a fast distortion correction and video mosaic method for large-apex-angle double-prism systems to achieve real-time imaging with a large field of view. The real-time distortion correction and video mosaic of a two-way rotational double-prism imaging system are performed by multiple camera pre-calibrations, the construction of a table-lookup-based interpolation re-projection algorithm, and the application of a multi-resolution fusion algorithm with image scale transform based on the search for the optimal seam. For the expansion of the field of view, we propose an evaluation method of the expanded field of view based on the law of refraction in the vector form, and the field angle expansion factor is used as the evaluation index. The simulation results show that the horizontal and vertical field angle expansion factors of the mosaic field of view can reach 1.50 and 1.30, respectively. The experimental results verify the feasibility of the proposed method and achieve real-time distortion correction and video mosaic at 30 frame/s.