The Back Projection (BP) algorithm does not use approximation in the imaging calculation process, and the imaging quality is high. Any array configuration is suitable for imaging. In recent years, it has been widely used in the field of radar imaging technology. However, in millimeter wave three-dimension holographic imaging, the computational efficiency is low, which affects the implementation of real-time imaging. Under the conditions of three-dimensional polar coordinates, the Fast Factorization Backward Projection (FFBP) algorithm uses sub-aperture division for imaging, which solves the real-time imaging problem to a certain extent. This article implements the FFBP algorithm based on the four threaded CPU and GPU accelerated CUDA platform, and compares and analyzes the imaging of multi-point targets. The results are basically consistent, thereby verifying the effectiveness of the accelerated algorithm. Furthermore, through electromagnetic simulation software, the resolution board is modeled and simulated to simulate real targets, and GPU accelerated imaging is performed. The calculation time is 33.97 times faster than the four threaded CPU, making it suitable for 3D near-field real-time imaging systems and better applied in the field of human security inspection.