Abstract: In view of the problems of typical unstructured, degraded characteristics and large-scale environment in coal mine tunnel, and the 3D reconstruction of coal mine tunnel is prone to low pose estimation accuracy and large cumulative drift error, a 3D reconstruction method of coal mine tunnel fused with lidar and inertial measurement unit (IMU) is proposed. In this method, the residual function of the lidar observation model and the prior state deviation of the IMU prediction model are tightly coupled through iterative kalman filter, and a more accurate posteriori state is obtained through state update, which provides reliable pose estimation for the degraded environment. In order to reduce the cumulative drift error in the process of tunnel 3D model reconstruction, a loopback detection algorithm based on Voxelized Generalized ICP (VGICP) is proposed. It is registered in a voxel-based single to multi-distribution mode, so as to complete the selection and accurate matching of loopback keyframes, realize the global pose correction of loopback keyframes, and effectively reduce the cumulative drift error of 3D reconstruction of coal mine tunnel. Compared with the A-LOAM and LEGO-LOAM algorithms, the proposed algorithm has significantly improved the accuracy and global consistency of pose estimation. Experimental results on public datasets show that the root mean square errors of RPE and APE of the proposed algorithm are 0.2718 and 0.5008, respectively, which are reduced by 53.14%, 50.97%, 48.31%, and 50.41%, 47.99% 47.49% respectively compared with other algorithms. Two real-world 3D reconstruction experiments are carried out. The results show that the error percentage of each area of the indoor corridor model constructed by the proposed algorithm in the directions of length, width and height was within 1.2%. The three-dimensional model of coal mine tunnel constructed by the proposed algorithm is consistent with the spatial distribution of the real coal mine tunnel. The overall distance degradation error is only 2.46%, which is 66.12%, 65.30% and 70.43% higher than that of the other three algorithms, respectively. Three-dimensional reconstruction experiments are carried out in the roadway excavation in the main laboratory of the coal mine. The results show that the average error percentages in the length, width and height directions are 0.47%, 0.75% and 0.67%, respectively. It can realize the accurate three-dimensional modeling of the tunnel.