Abstract: Water immersion ultrasonic detection technology is widely used in the internal quality detection of key aerospace components due to its high detection sensitivity and intuitive defect display. However, with the promotion and application of additive manufacturing, the outline of three-dimensional curved components is becoming more and more complex, showing the characteristics of space shaped surfaces. It is difficult for the existing water immersion ultrasonic detection system to realize three-dimensional display of detection images of three-dimensional curved components. In view of the above problems, this paper proposed a water immersion ultrasonic detection technology of three-dimensional curved surface components based on interpolation point copying modeling, realized the reconstruction of three-dimensional contour, three-dimensional space scanning path planning and detection image reconstruction, and carried out the verification of detection results with the help of three-dimensional curved blocks, realizing the effective detection of manual grooving and flat hole defects. The quantitative error rate of defects was controlled to be within 10%. On the basis of above, the actual testing and application verification of typical products were completed. The results showed that the proposed method can achieve the detection and quantification of the defects.