Abstract: A new non-destructive measuring method for the inner surface of 3D curved pipe is proposed. Sectional images of inner wall of the pipe are captured in real time according to the instruction while the sensor is moving along the pipe driven by a micro-robot. Image coordinates of the points in the section are calculated by an image processing algorithm. And the related 3D positions in the local coordinate system can be figured out based on the CCD camera calibration parameter. Accordingly the contour of the section can be reconstructed and the defects of the pipe inner surface are inspected. The coordinate data will be used for the reconstruction of the whole pipe inner surface subsequently.