Abstract: Azimuth preprocessing is the key to real-time SAR processor, the precision of computation in the azimuth preprocessing has an impact on the azimuth focus quality. According to the finite-wordlength characteristic, the errors, which are from quantization and multiplicative roundoff, and the effects on the performance of the pulse compression are analyzed. In this paper, firstly, several familiar quantization world.lengths are analyzed and the impacts on filter performance caused by different finite quantization wordlength are compared, at the last, the result of simulation after pulse compression is given.