The Jiuxi basin, located at the westernmost part of the Hexi Corridor, is a Cenozoic depression basin bounded by multiple groups of active faults. Many Holocene active faults have been developed in the basin. These faults played an important role in the coordinated absorption of the eastward expansion of the Qilian Mountains and the left lateral slip rate of the Altyn Tagh fault. The basin has a complex structure, and there is a tectonic setting for the occurrence of moderate-strong earthquakes. In recent years, many Holocene activities have been found in the inner and surrounding areas of the Jiuxi basin. Therefore, its seismic risk cannot be ignored. The Baiyanghe fault, with a length of 25 km and almost E-W trending, is located in the middle part of the Jiuxi Basin. The fault dips to the north with a dip angle about 25°. In a former research, the fault was deemed as a buried fault. Its continuous activity resulted in the deformation of the overlying terrace and the formation of the Baiyanghe anticline. According to the satellite image interpretation and field geological investigation, we found a continuous development of a low fault scarp in the west and middle segments of the fault, indicating that the fault is not entirely a buried fault, and some parts of the fault have reached the surface and become a broken surface fault. Two trenches excavated across the fault scarp revealed that at least two paleoearthquake events, aged about (8.7±0.6) ka and (3.9±0.5) ka, respectively, have occurred along the Baiyanghe fault since the Holocene. The vertical dislocation of the events was about 0.6 m. Using an empirical formula, we inferred that the magnitude of the earthquake was about 6.8.