Abstract: Aiming at the problems of low-grade small fault block reservoir with ultra-low permeability in Northeast Oil & Gas Company, such as low production rate and high development cost, which are difficult to form effective development, the distribution characteristics of remaining oil and its main controlling factors are studied, and the countermeasures of three-dimensional adjustment of flow field are put forward. The results show that the small fault block reservoir with ultra-low permeability has three kinds of remining oil enrichment characteristics and seven remaining oil distribution patterns, and the three-dimensional adjustment of flow field in different remaining oil distribution patterns can be realized by means of flow field adjustment countermeasures such as water well injection, edge water injection, injection-production adjustment and water well profile control and displacement. The application of the research results in the field has achieved good results and improved the development efficiency of low-grade reservoirs.