On the basis of the systematical monitoring and comprehensive analysis of the prestressed anchorage cable on the high slope of some hydropower station, the prestress loss during construction and after locking are studied, the relationship between the prestress loss and time is discussed, also the main influence factors of the cable prestress loss are researched. The conclusion is as follows: 1.The prestress loss is related with the tension stress. The stronger the force, the less the loss percentage ； 2.After being locked, the prestress loss can be divided into three stages: speedy decline stage, slow decline stage and relatively stable stage ； 3.The major factor that affects the prestress loss of cable in diluvium slope is the creep of the rock, the influences of construction and environment factors possess time effect ； 4.According to the monitoring data, it is proved that the disposal of the apparatus on provisional monitor section is reasonable.