Abstract: Asanewmicrowaveremotesensingmode，avideoSARcanprovideacontinuoussurveillanceoveraregionofinterest.ResearchesaboutspacebornevideoSARwerelimited.MostofcurrentresearchesaboutvideoSARonlyfocusonaircraftplatform.AspacebornevideoSARsystemwasdevelopedwiththetransmitterongeostationarysatellitesandthereceiveronthelowearthorbit（LEO）satellites.Therelationshipbetweentheimagingperformanceandthemainsystemparametershasbeenstudied.Thenanimageformationalgorithmwaspresented，whichcouldsatisfytheimagingqualityofvideoSARinhighsquintmodeandavoidunnecessaryduplicationofprocessing.TheDopplersmearandoffsetofthemovingtargetswerereflectedbytheprocessedimages.Meanwhile,thestationarytargetscanbefinelyfocusedon.

Key words: spacebornevideoSAR, bistaticSAR, echomodel, imageformationalgorithm, highsquint, dataoverlap