Due to the strong water sensitivity and dynamic vulnerability of loess, many strong earthquakes in loess areas have caused geological hazards such as liquefaction and landslides, resulting in serious casualties and property loss. Therefore, the liquefaction of loess with high water content under vibration can not be ignored. Based on previous studies, taking Dangjiacha landslide in Ningxia as an example, the liquefaction of high moisture content loess under vibration was studied in this paper. The field investigation results showed that the slip soil with high water content did not reach complete saturation (about 95%). Obvious liquefaction characteristics of "fluidization" were seen on the fresh core sample section. The performance and mechanism of liquefaction in the unsaturated loess layer of Dangjiacha landslide were analyzed with indoor tests and numerical simulation. The results showed that:(1) The mechanism of liquefaction in the unsaturated loess layer could be summarized as follows:the pore water pressure of saturated loess layer increases sharply under earthquake, while the growth response of unsaturated loess layer with high water content lags behind. As the pore water pressure dissipates upward, the groundwater percolates upward. When the average effective stress is close to 0, the liquefaction of unsaturated loess layer with high water content occurs. (2) The growth response of pore water pressure of loess with different saturation has time delay. According to the criterion of pore pressure ratio of liquefied saturated loess and Seed simplified discriminant method, it is confirmed that unsaturated loess layer with high moisture content in Dangjiacha landslide has a tendency for seismic liquefaction. The initial saturation ranges of soil liquefaction in the front and middle of the slope are 68.3%~100% and 73.8%~100%, respectively, and the soil in the rear edge of the slope will not liquefy.