Abstract: Taking the second Humen bridge as an example, this paper introduces the specific application of GNSS precision positioning technology in extra large bridges. When calculating baseline, the precision of the control network is improved by improving the precision of the approximate coordinates, choosing the appropriate solution strategy and reasonable constraints, so that the accuracy of the control network results can be improved, and the indicators meet the requirements. The measurement accuracy of the control network is further validated by the statistics of the survey results of Phase 8 of Humen Second Bridge. By calculating the poor coordinates of some points, the specific changes of the points are counted. The stability of the control points is evaluated by the single point test method, which provides a reference for other similar crosssea engineering control networks.