On August 2nd, tunnel shield machine “RenAo”, constructed by STEC Shanghai Tunnel Engineering Co., Ltd., of Zhuhai Maliuzhou traffic tunnel went smoothly through all the rocks in the sea, accumulating valuable experience and technical data to solve the problem of domestic and overseas projects with composite formation which is soft upside and hard downside. It also provides a reference for dealing with other projects with similar engineering conditions. Located in Zhuhai city, Guangdong province, Maliuzhou traffic tunnel, is the first super large-diameter shield tunnel with composite formation, which is constructed by the "RenAo" shield machine, of which the diameter is 14.93 meters and equipped with mud & water pressure balance device. The composite formation which is soft upside and hard downside is the biggest technical difficulty when constructing the project, and has brought unprecedented challenges to the tunnel shield constructing. After repeated deliberation, Shanghai Tunnel Corporation established an advanced pretreatment solution plan with the idea "to find, to explode and to block". The solution plan has been recognized by the distinguished expert group represented by academician Qian Qihu. At present, the project is nearly completed.