Based on the sedimentary character of six time cells in P1 Beierxi of Sabei developed region in Daqing oil field, this paper applies fuzzy mathematics method to divide reservoir flow unit. At present, there is no uniform division method, because flow unit is a fuzzy set with multi factor influence. There is great uncertainty among every influential factor, so does the influence extent of every factor to flow unit division. It isn’t objective to divide flow unit by one factor or simple congruence of several factors. However, the fuzzy mathematic method is fit to analyze the uncertainty relation in system or among systems. When the data of core well is in defect, applying the fuzzy clustering method to divide flow unit and combining development practice can reduce human factor greatly and make classification more objective and rational.