Abstract: The probability of pores produced in the laser welds are high when joining titanic alloy by Laser welding. The joint needs to be nondestructive tested for using in the aero fields. The parameters affecting C-scan image were given during the automatic ultrasonic inspection, such as the probe, the water path, amplitude, and the gate. The image of simulated pores in the welds was gained through testing the simulated sample and comparing with the radiograph. The experimental results showed that the defect, which was below surface with small roughness 1.0~2.5 mm depth and the diameter of which was bigger than 0.3 mm, could be found, when this testing process was used to detect the T-shape Ti alloy laser welding joint.