Abstract: HPAM/AlCit Colloidal Dispersion System(HACDS) is made up of polyacrylamide (HPAM) by certain concentration and aluminum citrate, was prepared for oil displacement in the stage of high water-cut. A series of experiments were carried out with the Core Flow Setup using man-made cores. Experiments show that the water flooding pressure was increased after a HACDS plug injection, and the oil recovery factor was increased by more than 10% on the basis of ordinary water flooding, the water-cut decreased obviously. repeated injection of HACDS may get worse oil recovery. The gelling time of HACDS in the core affects the oil recovery rate. The concentration of HPAM in HACDS must be suited to the permeability of the core used. This research is useful for field test of oil flooding by colloidal dispersion systems.