The IDA method for seismic fragility analysis has become one of the common methods to evaluate the seismic performance of building structures. In order to explore the seismic performance of the beam string structure with improved configuration of lower chord and brace, 15 sets of ground motion recording data recommended by ATC-63 are used to select the response-spectrum acceleration S_a(T1, 5%) of the first natural periodic structure of the earthquake motion strength parameter structure with a damping coefficient of 5%, and the vertical deflection of the maximum displacement point in the first-order mode shape is taken as the evaluation index for research. Based on the finite element software ANSYS, the structure is simulated, and the seismic performance probability of the improved configuration of the beam string structure under different damage states is analyzed by comparing the time course analysis results. The results show that in the face of large-scale earthquakes, the improved configuration of the beam string structure shows excellent seismic performance with significant anti-seismic potential and low risk of structural collapse.