Going through the development more than forty years, the overall water-cut to Daqing Oilfield has almost reached 90%. But there is still considerable residual oil in the place. Reservoir engineers want to know the residual oil spatial distribution and how to dig it. This requires large-scale reservoir simulation within limited time. Enlarged scale and highly expected efficiency need higher technical capability for reservoir simulation. By using PC-Cluster technique developed in recent years, large-scale reservoir simulation can be carried out at a relatively low cost. The first PC-Cluster used for reservoir simulation in Daqing Oilfield was designed and built. Based on this developing environment, the serial black oil simulator was parallelized by using the SLES components in PETSc. Then this parallel simulating technique was applied in seven oil production districts of Daqing Oilfield, where the PC-Clusters were configured and the parallel black oil simulator PBRS2.1 we had developed was installed and good results were achieved. In this paper, the hardware and system software configuration of PC-Clusters built is briefly introduced, the idea and method for parallelizing the serial black oil simulator is discussed, and the simulation study at seven typical field blocks and their application results are described and presented.