The Daqing oilfield has entered an extra high water-cut stage.In response to the production situations of sand bodies at late high water-cut stage under dense pattern condition in Daqing oilfield，and based on five core drilling observation wells with close spacing in Beierxi for major research object，the key technology was applied in quantitative characterization of intra-formational bed of channel sandbody on the basis of development demand and technical bottleneck of current intra-formational potential finding.The study defines some essential characteristics of core size heterogeneity，the main contents of which are intra-formational bed of the typical channel sand body.Different types of channel sand body internal sandwich lithology，thickness，sandwich distribution site，dip angle and residual oil distribution are different obviously.The proportion of inter-beds unidentified by logging to total inter-beds is 69.6%.The braided fluvial channel sediments of intra-formational bed in the stability of the sandwich are good，and the meandering channel is the worst.The study of distribution characteristics of intra-formational bed provides a reliable geological basis for releasing the internal remaining oil out of fluvial channel.