The Jishishan M6.2 earthquake occurred on December 18, 2023, induced many loess seismic subsidence disasters. Characteristics of the seismic subsidence disaster are obtained through the field investigation of disaster area in Qinyin Village, Shiyuan Town, Jishishan County. Physical parameters characteristics, microstructure characteristics, and seismic subsidence behaviours of the loess in Qinyin Village were studied based on a series of laboratory tests. In addition, the main causes of seismic subsidence disasters were analysed combined with the field survey results. The results show that the loess in the seismic subsidence area of Qinyin Village is cracked and the cracks are developed. The loess layer is destroyed by anti-dip step-shaped seismic cracking. The maximum settlement is approximately 57 cm. The maximum length of the crack is about 300 m, and the maximum width is about 83 cm. The edges of the loess ridge collapses or slides, and the maximum extension length of the collapse is about 100 m. The loess in the seismic subsidence area is loose, the moisture content is relatively high, the micro-trellis pores are developed, and the particles cementation is weak. Thus, the soil conditions for generating seismic subsidence are met. Besides, the thickness of the loess layer in the seismic subsidence area is relatively large, and the equivalent dynamic stress of the earthquake is greater than the critical dynamic stress to produce seismic subsidence of the loess, and the duration and the predominant period of the ground motion is large, which causes a serious seismic subsidence damage in the site.