Abstract: The numerical simulation method that is based on the dynamic damage responses of initially flawed steel structures is proposed.It is pointed out that the critical step is to solve the fractures of steel structures with working stresses lower than yield stress.In order to analyze the developing process from damaging to fracturing of steel structures,the sensitivity of the initially flawed steel structure used to predict the damage accumulation is presented.The initial crack is regarded as the sensitivity parameters,and the mathematical models are provided for the fatigue damage of steel structures.Numerical examples are presented to demonstrate the feasibility and effectiveness of the proposed method for the fracture resistance and fatigue life of steel structures with different initial flaws.The conclusions can offer guidelines for the security design of steel structures.