The Southern part section of Phase II Project of Line 8 of Beijing Metro,is located in central downtown area,has complicated surrounding environment and large design and construction difficulties. In this paper, the characteristics and difficulties of the project are analyzed.Key technologies,including shieldboring closely underneath existing Metro station, longistance shield boring underneath residual buildings,launching and receiving of shield machines of stacked tunnels, and Uturn and lifting of shield machine in mined cross gallery, as well as the designed program, technical innovations and technical countermeasures,are presented in detail. The paper can provide references for similar projects in the future.