To address the issue of highly localized blast loads caused by limited distribution layers in shallow-buried layered fortifications， an equivalent single-degree-of-freedom （SDOF） dynamic analysis method considering the characteristics of localized loads was proposed. This method was used for evaluating the response of the roof slab of supporting structural layers. Based on the selected mode shape functions and the energy equivalence principle， dynamic coefficient calculation methods for both elastic and plastic response stages of the structure were established. The validity of the method was verified through finite element simulations. Results indicate that the static deflection curve under uniformly distributed loads can still serve as the mode shape function under localized loads， with acceptable deviations. If localized loads are simplified to uniformly distributed loads for design purposes based on equal impulse principle， the maximum displacement of the structure may be significantly underestimated， with errors potentially reaching up to 9.7 times. In the plastic response stage of the structure， the dynamic coefficient of structural resistance is negatively correlated with the degree of plastic deformation， indicating that the more fully developed plastic deformation results in stronger structure"s ability to resist blast loads. The product of the total load duration and the structure’s natural frequency significantly influences the structural response： when this value is less than or equal to 1， the response is impulse-dominated； when it approaches 10， moderately extending the pressurization time favours structural resistance to blast loads； when the product exceeds 50， the beneficial effect of extending the pressurization tends to saturate. This method effectively characterizes the dynamic response characteristics of supporting structure layers in shallow-buried fortifications under localized blast loads， providing a theoretical support for the blast-resistant design of related protective structures.