Abstract: The ultrasonic testing of filling degree of grouting material in grout-filled hole and horizontal seam of precast concrete components is introduced. This method has the characteristics of nondestructive testing, and both testing position and ratio can be selected according to actual needs. Using transducers with high frequency and small diameter of radiation end is the key factor and the ultrasonic testing method with concentric circle equidistance is an innovation based on the traditional ultrasonic testing technology. With the judgment criterion by acoustic parameters of velocity and amplitude, the grouting defects in monolithic precast concrete building can be judged by comparing the data from the same testing region.