Abstract: Laser welding is an important method to join titanium alloy.The rigorous nondestructive test is necessary because pores are eaeily formed in the laser welding. The bad effects of uneven weld surface on the automatic ultrasonic inspection were summarized. The simulated practical sample was inspected through immersed ultrasonic testing technique at different point with different frequency probe. The defects images of weld were constructed using reasonable testing parameters and probe.The defect, which was located in 1.0-2.5 mm below the surface and whose diameter was bigger than 0.3 mm, can be detected, when the testing process was used to detect the Tshape Ti alloy laser welded joint.The experimental results show that a right frequency of probe can reduce the bad influence of uneven surface, which improves the reliability of ultrasonic test effectively.