It is essential to obtain a large amount of inverse synthetic aperture radar (ISAR) image data for ISAR automatic target recognition. For a super-resolution ISAR image for a complex perfect electric conducting (PEC) computer-aided design (CAD) model, parameter estimation methods should be applied to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times N$ </tex-math></inline-formula> scattered far-field data over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> frequencies and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> angles, which is conventionally obtained by using the shooting and bouncing ray (SBR) technique. Therefore, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> -time ray tracing processes are required for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> angles, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times N$ </tex-math></inline-formula> -time field calculations are required for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M$ </tex-math></inline-formula> frequencies. In this paper, to reduce the computation time for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times N$ </tex-math></inline-formula> -time field calculations, we introduce a fast scattered far-field prediction method for a super-resolution ISAR image of a complex PEC CAD model using the SBR technique. This method consists of two main ideas. First, under the small-angle approximation, we derive a DFT-based ISAR image formula in closed form, which allows the rapid acquisition of DFT-based ISAR image through just a one-time ray tracing process at the center frequency and angle. In addition, the scattered far-field data are also obtained by inverse discrete Fourier transforming the DFT-based ISAR image without <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> ray tracing processes and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$M \times N$ </tex-math></inline-formula> field calculations. Second, a field truncation method is employed to suppress errors in the scattered far-field data caused by the proposed closed-form formula. Further, by applying a parameter estimation method to the scattered far-field data, a super-resolution ISAR image is obtained quickly. Simulation results for complex PEC CAD models are in good agreement with the results for the conventional method, while the computation times are tremendously reduced.