Abstract: CO₂ breakthrough pressure plays an important role in CO₂ geological storage capacity, selecting target storage sites and assessing the safety of caprock. In order to explore the numerical simulation method that can be used to predict the CO₂ breakthrough pressure, a numerical method based on step-by-step method was proposed by using the numerical software of COMSOL Multiphysics, and the numerical simulation of CO₂ breakthrough pressure in a saturated low-permeability rock core were carried out. The results show that when the rock core is completely saturated with water, the breakthrough pressure and breakthrough time of CO₂ were 5.4 MPa and 70 h, respectively. Compared with the experimental results, it is proved that the numerical simulation is reasonable. Meanwhile, sensitivity studies on the interfacial tension in CO₂-H₂O systems and the key parameters of m/l values in van Genuchten (VG) model are carried out. The results show that, under the same interfacial tension, the greater the m/l parameters, the greater the CO₂ breakthrough pressure and time. In addition, with the increase of interfacial tension in CO₂-H₂O systems, the breakthrough pressure and time both tend to decrease. This study provides numerical information for further studies on CO₂ breakthrough in rock core and the evaluation of caprock.