Abstract: In Bohai Oilfield, a large number of oil and gas wells have entered the aging service stage, and the issue of sustained casing pressure caused by oil casing leakage has become increasingly prominent. To systematically investigate the influence mechanism of oil casing leakage defects on structural strength and accurately evaluate the safe service capacity of casings with leakage points, a numerical analysis model for casing leakage points is established based on the finite element platform, combined with elastoplastic theory. A systematic simulation analysis of casing structural strength is conducted under different leakage point shapes (holes, longitudinal cracks, and transverse cracks) and different sizes, and the relationship curves and mathematical expressions for the maximum equivalent stress of the casing as a function of internal pressure are fitted for the three typical leakage point configurations. The research results show that, due to the significant influence of the induced stress field at the leakage point, the pressure-bearing capacity of the casing decreases monotonically with increasing leakage point size, and the internal pressure threshold that must be strictly controlled during production. Under the same size and loading conditions, the risk of pipe string failure is much higher when the leakage point is a longitudinal crack than when it is a transverse crack or a hole. The established evaluation method for the strength of casings with leakage points achieves precise matching between leakage point parameters and the safe internal pressure threshold, providing a basis for risk classification, parameter optimization, and workover decision-making for wells with sustained casing pressure.