Abstract: Mobile LiDAR system is a multi-sensor integrated system, including laser scanner(LS), global positioning system(GPS), inertial navigation system(INS), and so on. Space registration is the key to get high precision 3D mapping. The installation angle error of LS is one of the main factors which influence the measurement accuracy. The related coordinate systems and transformations were introduced first. A method using vertical facade of a building wall to calibrate installation angles between LS and INS was proposed. A vehicle-borne LiDAR 3D mapping system was built to test the method.