A uniform linear motion is generally assumed in traditional synthetic aperture radar(SAR) processing algorithms. However, it is inevitable that if there is 3-D acceleration, the image formulation processing complexity will be significantly increased, especially in highly squinted situations. This paper aims to handle the imaging problems in the highly squinted SAR with three-dimensional acceleration, which utilizes the Taylor formula to expand the distance equation and further resolve it. Based on the formulated range formula, we further utilize the two- dimensional non-uniform Fast Fourier Transform (2D-NUFFT) to obtain focused SAR imagery. The proposed methods are verified with simulation results.