As an important component of the water diversion pipeline in the power plant building，the stable and reliable operation of the steel bifurcation pipe is the key to the normal operation of the entire water diversion pipeline and even the power plant. Stress and deformation are the focus of monitoring the water pressure test process of steel bifurcation pipes，and they are also important criteria for determining whether the test is terminated. The article takes the buried steel bifurcation water pressure test of a pumped storage power station as an example to monitor the stress and deformation during two water pressure tests，and compares and analyzes the monitoring data. The test data shows that the stress and deformation monitoring values of most measuring points have a good linear positive correlation with the test pressure，and the measuring point N10 showed an abnormal situation of stress decrease during the pressure rise stage. In two water pressure tests，when the test pressure was 6.0 MPa，the maximum equivalent stress of the steel bifurcation exceeded the stress limit，and the test was terminated in a timely manner，which ensured the safety of the steel bifurcation structure and provided references for similar engineering projects.