Abstract: At present, the capillary force test method cannot reflect the dynamic change of capillary force in the process of porous flow.To solve this problem, the concept of oil-water two-phase dynamic capillary force was put forward on the basis of gas-water twophase dynamic capillary force, and the dynamic capillary force test unit was prepared.The pressure sensor to measure oil phase and water phase independently was developed respectively by using the semi-permeable membrane.8 pressure testing points were set symmetrically on two surfaces of the artificial core, and oil-phase pressure sensor and water-phase pressure sensor were fixed firmly to the artificial core with epoxy resin.The experimental process was similar to the one that is used to measure relative permeability curve by means of steady state method.Oil-water mixture was injected at the constant proportion and the capillary force under different saturations was measured.The dynamic capillary force on the artificial core was measured by means of the dynamic capillary force testing unit, and the dynamic capillary force curves corresponding to 3 displacement velocities were plotted.It is indicated that the numerical value of capillary force varies with the displacement velocity and has more effect on the numerical calculation of water displacing oil process.