This study simulates the seismic disaster scenario of the 1920 Haiyuan earthquake. Utilizing a ground motion parameter attenuation model based on the shortest distance to the rupture fault, seismic intensity distribution was simulated by integrating records across different epicenter locations and magnitude ranges. A dual-model approach incorporating multiple scenarios was employed to estimate casualties in the event of an earthquake recurrence, with simulation accuracy validated against historical seismic damage records. The results show that the intensity distribution derived from the epicenter location and focal depth provided by the Lanzhou Institute of Seismology, combined with a magnitude of 8.3, closely matches the historical isoseismal map, and the extent of the meizoseismal area aligns well with the surface rupture zone. Casualty estimates indicate that, under current population and socioeconomic conditions, a recurrence of this earthquake could still cause hundreds of thousands of fatalities, predominantly concentrated in zones of intensity IX and above. Key contributing factors include the inadequate seismic resistance of buildings in the meizoseismal area, high population density, and earthquake-triggered secondary disasters. Comprehensive risk mitigation strategies-such as active fault avoidance, stricter enhancement of seismic building codes, and improved emergency preparedness planning—are therefore critical to reducing future losses.