A modified load curtailment model based on dynamic correction area and static Ward equivalent method is proposed to improve the calculation efficiency of power system reliability assessment. Firstly, an analytical expression of cross-weight for node was deduced using Wood Bury matrix transformation, on the basis of which the dynamic correction area that reflected the effective adjustment area for overload lines was determined. Secondly, a static Ward equivalent method of considering equivalent slack node was developed, thus realizing the flexible equivalence of external network of dynamic correction area. Furthermore, a modified load curtailment model for dynamic correction area was presented. The proposed model transforms traditional load curtailment method which is a global optimization, to a series of consecutive sub-optimizations in the dynamic correction areas, reducing the optimization scale and improving the calculation efficiency greatly. The effectiveness of the proposed method is verified by the simulation results of RBTS, IEEE-RTS79 and IEEE-RTS96 systems.