Abstract: In the process of engineering construction, there was a great difference between the test condition and the operation working condition when the pipe was tested by hydraulic test, which made the safety problem of the pipe outstanding in the hydraulic test. In the hydraulic test of the steel bifurcated pipe and the distributing pipe of hydraulic turbine, acoustic emission monitoring technology was used to dynamically monitor the defect deformation and crack propagation of pipe in hydraulic test. The effect was obvious, and its experience can be referred for similar projects.