The wave velocity is the main physical parameter of ultrasonic wave CT test
it can distinguish the change of strength and density in reinforced section. The absorption coefficient is the main physical parameter of electromagnetic CT; it can determine the distribution of the reinforced section. CT has been applied to evaluate the grouting effect of group piles in Su-Tong Bridge. According to the results of coring and CT test
it is practicable to apply ultrasonic wave CT and electromagnetic CT synthetically to test the grouting effect of overlength piles.