In order to reduce the requirement of original point cloud preparation for the axis extraction of shield tunnel, a feature extraction method of point cloud is introduced in this study. Firstly, the ring joint point cloud of shield tunnel segment was identified based on the extraction method of crack point cloud with the distance difference feature. Then, the curve fitting of the interstitial points was carried out by the least square method. At last, the central axis of the tunnel is extracted on the basis of the circular seam curve. Experimental results show that the point cloud extraction method based on the distance difference feature can effectively identify the ring seam point cloud, and fit the tunnel central axis on the basis of the ring seam point cloud. Compared with the traditional extraction method, the proposed method is faster, and the extracted central axis is more spatial.