Abstract: In order to guiding the horizontal well waterflood development of the Putaohua oil reservoir which is low abundance and ultrathin, the numerical simulation research in the horizontal well area and the analysis of the distribution of the remaining oil is carried out. In this paper, the numerical simulation research in the horizontal well area and the analysis of the distribution of the remaining oil using the three-dimensional geological modeling data of the thin, poor reservoir is discussed. The analysis of the sensible reservoir characteristics have been conducted using Mepo software. The accuracy of simulation has enhanced because that the horizontal well development status has be simulated using grid refinement techniques. The project which is basing on research results of numerical simulation and remaining oil guided horizontal well waterflood development efficiently.