Daqing Oilfield is the most important and the biggest oil field in China, with forty five years water flooding development, the reservoir in Xing6 area is in high water cut stage of development. The scatter distribution of remaining oil and the poor development on thin and poor oil layers are present problems. After the adjustment of secondary infilling implemented in 1996, the recovery degree of low permeability and thin layers has been improved, but the development on tabulated thin reservoir (effective thickness between 0.2 to 0.5m) is still poor, especially the un tabulated reservoir (effective thickness below 0.2m). In response to the sand layers with effective thickness below 0.5m, the tertiary infilling stage is implemented. On the basis of elaborate reservoir geological description, and using the skills of comprehensive description of the remaining oil, we analyze the features of remaining oil, as well as all types of layers washing condition and adjustable sandstone thickness after secondary infilling in Xing6 area. The results indicate that the Xing6 reservoir has certain potential for tertiary infilling adjustment. In this paper, we adopt the three combinations policy, combined tertiary infilling adjustment with original well pattern, combined tertiary infilling adjustment with water flooding regime modification, and combined tertiary infilling adjustment with later tertiary oil recovery, to optimize well distribution. Through the adjustment of the well pattern, injector producer distance, well density, water flooding system, etc., the perfect water flooding regime is achieved to fully produce the remaining oil of the sand layers with effective thickness below 0.5m. The good results have been achieved in Xing6 area. After the adjustment of tertiary infilling, the Xing6 area recovery ratio increases 2.72%, the flooding control degree of tabulated thin reservoir (effective thickness between 0.2 to 0.5m) and un tabulated reservoir (effective thickness below 0.2m) increase 4.23% and 9.69%, and formed the matching tertiary infilling techniques.