The prestress anchor cable support in large deformation tunnel has received great attention in recent years. For the problem of prestress loss of anchor cable in tunnel surrounding rock support, the mechanism of prestress loss of anchor cable in tunnel surrounding rock support and the influencing factors were revealed through field test and theoretical analysis. The results show that the locking loss during tensioning and locking was mainly affected by four factors: tensioning equipment and process, anchorage friction, anchorage loss and anchorage system retraction; after the anchor cable is locked, the surrounding rock and anchorage structure are continuously deformed by the anchor cable prestress until stability, and the coordinated deformation includes the coordinated deformation of the inner anchorage section, the coordinated deformation of the outer anchor head and the coordinated deformation of the group anchor head. The design of anchor cable anchorage system for supporting the surrounding rock of large deformation tunnels and engineering construction suggestions are proposed to provide reference for the future application of prestressed anchor cable structure in similar engineering structures.