Abstract: Concrete piling hole detection is an important step in ensuring the quality of pile foundations. In this paper, to address the difficulty in evaluating hole quality due to the sparse measurement points of existing testing equipment, a drilled pile hole detection system based on ultrasonic technology is designed. The detection probe of the system consists of 12 high-frequency, broadband, and sharply directional ultrasonic transducers that are flat, thin, and small in size, arranged in a layered and dense array. This design improves the accuracy and density of measurement points. Tests show that compared with traditional hole inspection equipment, the system can collect high-density hole wall contour data and support three-dimensional imaging of the drilled hole morphology, thereby significantly improving the accuracy and intuitiveness of hole evaluation.