Abstract: The faulted structural strata are usually constituted by numerous fault-blocks in faulted basin.In the extending process,each faultblock is a comparatively independent sedimentary and subsidence center.In the process of rift-subsidence evolvement,some fault-blocks succession rift and subside for a long period,becoming the host sags of the primary oil source center,and the others show the less range of subsidence or strong denudation,becoming the brink sags,all these just because of the difference in structure position,boundary fault strike,and dynamics characteristics.According to the formation and the function in structural activity,the brink sags can be divided into abandoned-type,adjusted-type,transitional-type,and reconstructed-type.