Abstract: For the demand of auxiliary driving, a vehicle-mounted LIDAR system was built to scan road scene. A set of method for calculating road parameters was designed based on 3D LIDAR point cloud, including road width, bridge or tunnel height limitation, turnaround radius and so on, which provided decision basis for auxiliary judgment of road passability. Experiments and comparison tests show the stable performance and satisfactory accuracy of algorithms, which have advantages of efficiency and automation, and also can provide useful decision parameters for auxiliary driving.