Abstract: Aiming to evaluate inner quality of TaW alloy plates about 1.6 mm(thickness)×80 mm(width), using the manufactured 1.25P15×20 38° type ultrasonic transducer, the testing experiment has been actualized by lamb wave method. Its frequency was 1.25 MHz, an angle of incidence was 38°, and the size of wafer was 15 mm×20 mm. The sensitivity test results indicated that not only the defect about  0.4 mm in plate could be finded using this transducer, but also between the hole diameter and lamb wave amptitude was shown linear relation. It fulfilled quality demand of production.