This paper introduced present application in the world and some problems in the calibration technique of 3D measuring system. Auto-calibration technique of multiple targets tracking for detecting outline based on random placement and regular number is put forward. At the same time, the concrete algorithm is given. Then, according to the algorithm, the corresponding experimental result is obtained. Furthermore, the calibration accuracy is compared and analyzed. Finally, it comes to a conclusion that this algorithm can make the operation more simple and convenient. And the calibration accuracy is kept within 0.03mm.