Abstract: This paper analyzed the influence of the ultrasonic head wave amplitudes change to the concretes sonic time value, and studied the relationship between the ultrasonic wave instrumentation head wave amplitudes change and the predicted value of concretes intensity. The result showed that the false positives of measured sonic time value caused by the ultrasonic head wave amplitudes difference, had led to large error in concretes intensity measure. In order to reduce the mistake of sonic time value, it must stipulate head wave scope read sound when calculating concretes intensity.