A mega-gear positioning method based on laser tracker multi-station measurement was developed to improve the positioning accuracy of a mega-gear measuring system based on laser tracker and to ensure the positional and attitude relation between measuring instruments and a gear. The redundant data provided by laser tracker multi-station measurement were used to solve the optimally collinear equation between two points and to establish a multi-station measurement model based on laser tracker. Then, the singular value decomposition was used to correct the conditional number of analytical matrix in the multi-station measurement model. Experimental results show that the standard deviation mean of the distance between different station points obtained by the multi-station measurement mode is 0.008 mm, which is much less than that (0.024 mm )measured by directly measurement method at different stations. These data mean that the multi-station measurement model has a high control ability for measuring precision. The research improves 3D measuring precision of gear positioning and provides a reliable data source for establishing gear coordinate models of the mega-gear measuring system based on laser tracker.