Abstract: The Qiantang River Tunnel, which is currently under construction, stretches beneath the Qiantang River and occupies a dominant position in the Qianjiang Crossing and Connection Project, which is an important part of the highway project in Hangzhou. The tunnel is located at the mouth of the Qiantang River, and the geological and hydrological conditions are very complex. The section beneath the river was constructed using a shield with a diameter of 15.0m, which makes it the world's largest shield tunnel. This paper describes the overall design scheme of the Qiantang River tunnel, the construction environment, construction standards, the tunnel plane, the profile and cross-section arrangement, etc. Some key technologies are also elaborated upon, including the structure and waterproofing of the large-diameter shield tunnel, the shielding beneath the river with shallow overburden, the deep foundation pit in soft soil, the three-dimensional parallel operation of the shield section and the comprehensive hazard prevention system.