Abstract: The deformation behaviors of water conveyance tunnels under high internal pressure can scarcely ever be accurately evaluated using existing monitoring technologies.A full-scale experimental test, based on the project of water resources allocation in Pearl River Delta, was conducted to investigate the deformation mechanism of the superimposed linings consisting of a concrete segment, self-compacted concrete, and steel tube.The distributed fiber optic sensing was used to monitor the performance of superimposed linings under high internal pressure.The test results show that the strain development of the linings presents the character of discontinuous variation during loading.The steel tube generates elastic deformation, and the strain change is small.The deformation process of self-compacted concrete can be divided into two stages: elastic deformation and plastic deformation.The plastic zone gradually expanded from the concrete surface to the deep layers forming several cracks at the segment splicing joint.The spaces between some segments on the crown of the tunnel are prone to enlarge under high uniform internal pressure.The deformation characteristics and failure patterns of the superimposed linings were revealed in the view of strain measurement.This study verifies the great application potential of distributed fiber optic sensing in the water conveyance tunnel.