For Light Detection And Ranging(LiDAR),Inertial Navigation(INS) and Global Navigation satellites system(GNSS) integrated navigation and positioning systems,the sensor mounting location needs to be calibrated before the sensor data is fused.Aiming at the above objectives,this paper proposes a method based on fragmented iterative method and KD tree optimization DBSCAN algorithm to find the optimal placement parameters.After the initial measurement parameters are roughly measured,the values near the initial parameters are iterated by the fragmented iterative method,and the DBSCAN algorithm based on the KD tree optimization is used to evaluate the coincidence degree of the adjacent frame points in the unique coordinate system,and the best accurate placement parameters is obtained.The experiment uses Iterative Closest Point(ICP) algorithm to compare the calibration parameters of different stepsizes.The experimental results show that the accuracy of the placement parameters is slightly improved in the case of reducing the step size.The method used in this paper improves the calibration accuracy compared with the initial estimation of external parameters.