The underground distribution of remaining oil in the ultra-high water cut stage is growing complex，and it is more and more difficult to tap the potential. Clarifying the development potential of the remaining oil is the basis for enhancing the oil recovery of reservoirs in the ultra-high water cut stage. Considering the spatial distribution，enrichment，water consumption characteristics，and economic mobility of the remaining oil in the ultra-high water cut stage，the recoverability coefficient and recoverable potential factor of the remaining oil were proposed from the aspects of recoverable resources of remaining oil and regional development potential to construct a comprehensive index set for the classification and evaluation of remaining oil in the ultra-high water cut stage. On this basis，the fuzzy C-means clustering（FCM）algorithm was improved by the Xie-Beni function to conduct an unsupervised clustering evaluation of the remaining oil in the ultra-high water cut stage. As a result，a new classification and evaluation method of the remaining oil in the ultra-high water cut stage was formed. With the north of the west area of Gudao Oilfield as an example，the research on classification，evaluation，and potential adjustment of remaining oil in the ultra-high water cut stage was carried out. The results show that this method can accurately determine the dominant position of the remaining oil potential. According to the evaluation results of various remaining oil potential of north Ng3-4 unit，corresponding potential tapping measures were proposed respectively，which guide the well pattern exchange and flow line adjustment between unit strata. After the adjustment，the recovery of this unit increases 2.1%，and the recoverable reserves increases 29×104 t.