Through model test and engineering application,the paper studied the application technology of IES test method in the detection of concrete defects existing in the port structure.It studied the influences of parameter setting,operation steps,defect size,defect depth,and columnar components in this method on the stress response through model test and got the following conclusions:1)The defect judging method is mainly based on the deviation of main frequency and supplemented by that the frequency-domain curve appears secondary peak;the threshold value can be fixed as 5%.2)Defect size is positively correlated with the deviation of main frequency;defect depth has a threshold value;shallow depth produces small influence on the deviation of main frequency, and when the depth exceeds the threshold value,the defect depth is in direct proportion to the deviation of main frequency.3)As the effective detecting depth of IES system shall be less than 1 m,so it doesn’t apply to the columnar member.On this basis,this method was applied in the detection of precast concrete unit at a high-pile wharf.The defect inside the concrete could be recognized intuitionally and quickly by detecting the thickness cloud picture.