Abstract: Fixed-point processing optimization can reduce the storage, improve the computing speed, is an effective way to reduce power consumption and storage, improve the real-time performance of synthetic aperture radar (SAR) real-time imaging system. Taking the well-known chirp scaling (CS) algorithm as example, the count of computations was analyzed in this paper. Radix-2<sup<2</sup< algorithm of fast Fourier transform (FFT) as the main part of computations was adopted for fixed-point processing optimization, realized through a reasonable scale strategy with SystemC. Thus rapid system-level simulation of CS algorithm was implemented to provide a standard basis for FPGA implementation. Finally, test images from the raw lattice and area target data (16 384×16 384) were analyzed using fixed-point CS algorithm with 24 bits input word lengths. The simulation results meet the requirements of system indicators.