Abstract: Four pieces of prefabricated shear walls with different types of grouting channels were designed and prepared. Grouting were carried out according to the design conditions after the test pieces being assembled. There were artificial defects such as voids and impurities in the grouting channels. Dry coupled phased array ultrasonic (DPAU) in form of tomograph output, 2D image processed after linear scans and synthetic aperture the focusing technique (SAFT), were used to detect the defects in each grouting channel. Inspection results show that the first two methods can accurately detect the defects, such as positions and sizes of voids (whose error is within 15 mm) and impurity location and size (whose error is within 10 mm) in tubeless, PVC pipe and steel pipe grouting channels. The SAFT can reduce the human error and improve the accuracy of defect location and size recognition, and its recognition error is 40%-100% lower than the 2D image method. DPAU can clearly identify the position of voids in the metal bellows, while the dense parts may be partially misjudged.