Abstract: The inverse proportion relation between azimuth resolution and width of the swath of single aperture space-borne SAR is analyzed.In order to resolve this problem,a novelty method is presented in this paper,which adopts lower PRF and achieves high azimuth resolution and wide swath together by assembling and processing the sampling data from all small satellites.The relationship between the number of satellites,azimuth resolution and width of swath is analyzed in detail,and the interval formula of distributed small satellites is presented.The result shows that the width of the swath for a multi-aperture SAR system including 2N-1 small satellites in line is N times larger than that of a single-aperture SAR if they have the same azimuth resolution,which improves the observation performance of SAR hugely.