Abstract: According to the testing requirement of small diameter tungsten alloy bar,the ultrasonic test block is designed after analyzing the possible defect type in bar molding technology and combining ultrasonic testing technology with testing quality requirement.And different reflectors in test block are distributed reasonably by theoretically calculating result.The used results show that the test block realizes sensitivity adjusting functions of ultrasonic immersion longitudinal wave and refraction transverse wave at the same time,and its applying range includes all dimensions of the tungsten alloy bar,and its function and advantage satisfy the requirement of products test.