The concrete-filled steel tubes (CFST) structures are increasingly widely used in super high-rise buildings. Due to inadequate construction quality control and the shrinkage of concrete materials, the mechanical behavior is negatively affected by the possible concrete core defect and the interface debonding between the concrete and the steel tube. In this paper, for the purpose of detecting the defects in CFST, the piezoelectric ceramic plate is mounted on the surface for measurement, and the influences of these two internal defects on the responses of the piezoelectric ceramic plate on different test paths are tested and numerically simulated. By comparing the output signals of the piezoelectric sensors on different detection paths of different specimen that are healthy and have concrete core defect and interface debonding defect, the effects of the defects on the stress wave propagation are investigated and the sensing range of detection with the patch and catch method is obtained. The results show that the proposed method can effectively detect the effects of the concrete-filled steel tube, and the determination of the sensing range provides a reference for the sensor arrangement in engineering application.