Abstract: The SAR raw signal simulator in the time domain by the target-by-target method is inefficient, while the simulator in the two-dimensional (2-D) frequency domain can not be directly used to generate the Terrain Observation by Progressive Scans (TOPS) raw data. As for this issue, an efficient TOPS raw data simulation approach is proposed. In the range direction, the 1-D convolution between echoes of referenced point target and scattering coefficient of the imaged scene is introduced, while raw data is simulated and stored by the pulse-by-pulse method in azimuth. The processing steps of the simulator are given in detail, and its computational complexity is analyzed. Simulated echoes of the proposed simulator and the accurate time domain simulator are compared. Finally, the imaging and interferometry results of the simulated data are given to validate the effectiveness of the proposed approach.