Abstract: The three coordinate measuring machine and position measuring gauge are inefficient, expensive and can not meet the requirements of on-line detection. For these reasons, an on-line measurement system for the hole group position of battery packages is constructed, which is composed of marble platform, linear motor, 3D line-scan camera and so on. As a part of the battery pack production line, after the battery pack is put into the detection platform by the manipulator, the linear motor drives the 3D line scan camera to obtain the 3D point cloud data of the battery pack box hole group. The 3D point cloud is projected to the calibration plane, and the noise reduction pretreatment with median filter is used to extract ROI by dilating and corroding the outline of the detected hole. The outline is extracted by Canny edge detection, and the features are extracted by least square method to obtain the center coordinates and the radius of the assembly hole. The data obtained are corrected by flexible positioning method. The results show that the on-line positioning system of battery packages can meet the measurement requirement of 0.2mm positioning of battery packages.