The 2021 Yangbi MS6.4 earthquake in Yunnan Province is the strongest seismic event in the region in recent years and has generated intense strong ground motions that caused significant casualties and property damage. Numerical simulations were conducted on the strong ground motion to deepen the understanding of its characteristics. A 3D geological model incorporating actual topography and a fault weakening model with elastic material properties were used to simulate dynamic rupture. Results demonstrate that the rugged topography of the Hengduan Mountains considerably influences the strong ground motion distribution of the Yangbi earthquake, with an amplification effect at the ridges and steep slopes where the elevation changes abruptly. When preseismic stress fields are introduced through boundary conditions and variations in fault material strength before and after the earthquake are considered, the simulated strong ground motion-including its magnitude, distribution, and attenuation rate-closely approximates the actual event. Simulated results of peak ground acceleration (PGA) and acceleration response spectrum at near-field stations align closely with the observational records. PGA contours correspond closely to the seismic intensity maps in spatial distribution. Integrating realistic topography with dynamic source modeling can enhance the simulation reliability for seismic hazard mitigation and resilient urban planning.