Abstract: Process characteristics of the ultrasonic testing in the electric resistance welded pipe production were introduced in this paper. The selection of technological parameters was discussed from three respects, such as refraction angle, width of the acoustic beam and ultrasonic frequency. In the ultrasonic testing of the ERW seam, the lower limit of the refraction angle is 33.2°, and the upper limit increases with the increment of the ratio between inter-diameter and outer-diameter. The refraction shear wave with the angle of 45°can detect the surface-breaking defects effectively. To detect the inner area type defects, shear wave with large angle should be adopted. In practice work, the width of the incident beam is determined by the refraction angle and the pipe diameter to avoid the generation of the surface wave and the refraction longitudinal wave.