In response to the unsuitability of infilling potential evaluation method in an extra-high water cut stage in field, we analyze the oil field development process on the basis of the variation of the well network density conditions and infilling development effect.Based on the research, we establish the rule of well spacing density for infill wells to increase recoverable reserves, and combined with the economic limit of single well recoverable reserves in different prices, we propose a new infill potential evaluation method. The infilling method for extra-high water cut stage oilfield has better adaptability, and is able to guide the infilling potential evaluation for oilfield at extra-high water cut stage.