With finite difference code Flac3D, the stability of loess slope with hidden hole at different locations has been evaluated. Failure mechanism of loess slope is also studied. Under plane strain conditions, the results of numerical simulation show that the existence of hidden hole has a direct impact on the stability of the loess slope, and sometimes decreases the safety factor. The failure of hidden hole also directly affects on the overall destruction of slope. Consequently, at the stage of loess slope design, it is necessary to carefully evaluate the stability of loess slope with hidden hole. Particularly, it is important to consider the influence of stability by the position of hidden hole in loess slope.