The auxiliary pipelines are divided into regional blocks,ultrasonic non-destructive testing technology is adopted to carry out single-point excitation and multi-point detection,collect ultrasonic time-domain signals of ac-tual auxiliary pipelines,analyze and process the detected time-domain signal data,and thus obtain information about the internal structure of auxiliary pipelines.Cubic spline method and local weighted scatterpoint smoothing method are used to reconstruct the time domain signal data respectively.The results show that the linear interpolation method is better than the local weighted regression method in 3D reconstruction effect,and it can realize the accu-rate reconstruction simulation of auxiliary pipeline defects.