According to the survey and design study of Xiamen Subsea Tunnel scheme, the author gives a primary discussion on key construction technologies of Qiongzhou Channel Tunnel, Bohai Strait Tunnel and Taiwan Strait Tunnel. In order to build the above subsea tunnels successfully, we must achieve technology breakthrough in seacrossing control survey, geological survey under deep ocean, excavation and lining in fault stratum with high water pressure, rapid tunnel excavation technology and ventilation of extralong tunnel unit.