High filling slopes are widely used in highway and water conservancy projects in mountainous areas. Excavating steps and prestressed anchor cable support can improve slope stability. Taking a high filling project in mountainous area as an example, stability and deformation law of high slope was analyzed with the consideration of earthquake situation. The results showed that most dangerous failure surface of slope was arc-shaped, with displacement peak value of horizontal and vertical located at the foot and top of slope, respectively. The pore water pressure was reduced on slope surface due to pore water discharged from slope under earthquake situation, while the variation of pore water pressure in the slope interior had little effect to the slope stability. When the peak acceleration was 0.20 g, shear failure appeared to the rock mass above the interface, and fracture surface of slope at all levels runed from the top to foot of slope, and rock slope was unstable.