Abstract: Based on the phased array technology, the inspection technique was established for nuclear power fir style turbine root.By analyzing the stress of blades, the most probable area of defect was found. The sound field simulation was applied to quantify the relationship between parameters of phased array probe and the probe acoustic field generated. And the relationship was used as a basis for designing a dedicated phased array probe.Scanning modes were designed for different inspection zone.The experiment was performed on the specimen to prove the effectiveness of the technology .The corresponding phased array inspection technology was formed eventually. The actual project will be applied to prove the reliability of the inspection techniques.