After 5·12 earthquake in Wenchuan, the slope stability has been severely damaged in earthquake area, many destroyed modes appeared, such as collapse, landslide, deformation, and so on. Pre-stressed anchor cable is the main method of preventing high slope harm, with large tonnage pre-stressed cable anchoring in stable rocks of slope to resist the deep slope failure and deformation by pre-stressing. It is important to monitor the pre-stress variation, through the pre-stressed state monitoring both in and after construction process, the reinforcement effects can be tested and based on the long-term monitoring results to evaluate the slope stability state, whether to take appropriate remedial measures can be decided. According to the slope anchor cable reinforcement of Futang hydropower station after earthquake and the stress monitoring, the paper discusses the stress loss of pressure-dispersive anchor and the variation rule.