A large number of sudden loess landslides have been developed in Heifangtai area of China. The process of deformation and failure of these landslides is accompanied by significant excess pore water pressure. Through field investigation, the characteristics of these landslides are generalized and the model is established for indoor physical simulation. The process of deformation and failure of these landslides is restored, and pore water pressure and displacement are analyzed. The results show that the pore water pressure produced by groundwater before landslide deformation needs to reach a certain degree, and there is a sustained slow creep before slope failure. During this period, the pore water pressure behind landslide body fluctuates and causes accelerated deformation, which further promotes excess pore water pressure in the inner part of landslide. Finally, the obvious excess pore water pressure of the soil leads to the instability and failure of the landslide. The static pore water pressure produced by groundwater in Heifangtai is the cause of creep deformation of sudden landslide, and the fluctuation of pore water pressure caused by creep deformation is the inducement of the sudden increase of landslide deformation and instability damage.