In order to improve the precision of laser tracking measurement for mega gear, a combined measuring network for mega gear was established by combining laser tracking device and flexible joint coordinate measuring arm. The coordinate transformation relationship between the global coordinate system of laser tracker and the coordinate system of flexible joint coordinate measuring arm was determined by using the frog jump technology to realize the spatial registration of measurement data at different stations. A multi-dimensional measurement method of laser tracker was introduced, which had abandoned the angle measurement module, a multi-dimensional measurement position parameter calibration model of laser tracker was established, redundant data were measured and L-M optimization iteration was carried out in this method in order to improve the global control accuracy of laser tracker. The simulation experiment of combined measurement network was carried out, and the measurement data were analyzed and compared. The average error of combined measurement network was 0.007 mm and the error standard deviation was 0.004 mm. Under the same conditions, the average error of direct measurement method using laser tracker was 0.044 mm. The simulation results show that this method can improve the measuring accuracy obviously and meet the requirements of the measurement of tooth shape of mega gear. It has a good theoretical and engineering application value.