As a special working mode, the circular scanning Synthetic Aperture Radar (SAR) is widely used in the earth observation. With the increase of resolution and swath width, the simulation data has a massive increase, which boosts the new requirements of efficiency. Through analyzing the redundancy in the raw data simulation based on Graphics Processing Unit (GPU), a fast simulation method considering reduction of redundant computation is realized by the multi-GPUs and Message Passing Interface (MPI). The results show that the efficiency of 4-GPUs increases 2 times through the redundant reduction, and the hardware cost decreases by 50%, thus the overall speedup achieves 350 times than the traditional CPU simulation.