Abstract: Presently, the pre-stressed anchor already has been obtained widespread application for the foundation pits supports project. However, the rule of pre-stress changes after anchor is locked have not been researched thoroughly; especially when the foundation sidewall is soil slope. The rule of long time and short time pre-strssing losses is not awared clearly. Monitoring data shows that the load changes with time can be described as three phase. Phase I, instantaneous losses of load during the lock of operation.Phase II,,load slowly growth. In phase III, the load is almost uniform.