Terrestrial laser scanning has been widely used in tunnel engineering，the extraction of tunnel cross sections is often based on tunnel centerlines，which is the most difficult part.A novel method for automated extraction of tunnel centerlines was presented in this paper.In this process，the boundary points of a tunnel are extracted from tunnel point clouds，the inliers for multiple model fitting are estimated from tunnel boundary points using RANSAC （RANdomSAmple Consensus） algorithm，the final centerlines are determined using a global optimization based on a re-sampled algorithm.The proposed method was applied in the Xieziyan tunnel in Sichuan.The results of application showed the extraction of tunnel centerlines achieved a high accuracy.The RSME of centerlines fitting was 16.5mm.Compared with total station surveying，the RMSE of the deviations was 10.3 mm.