The square inverted nine-spot pattern is widely used in Wangyao low permeability oilfield, and the infilling pilot is carried out in the west part. In order to evaluate the EOR potential of pattern infilling program, the infilling inverted nine-spot pattern physical simulation program is designed. Considering the geological features of pilot area, the natural sandstone outcrops are selected, which have the similar porosity, permeability, oil displacement efficiency and throat radius for the waterflooding experiment. According to the actual timing and manner of infilling adjustment of the pilot area, we simulate the infilling injection during the experiment to study the impact of infilling adjustment on development performance. Results show that, after infilling adjustment, the EOR is increased by about 4.94%. If the infilling timing is postponed for five years, the EOR might reduce by 1.2%. Therefore, the infilling adjustment should be implemented as soon as possible in the pilot area.