With the modern process of city, subway becomes the best choice of resolving the traffic jamming because it is convenient and effective and well-environmental. As so far, there are three kinds of subway construction methods (shield tunnel, hidden excavated tunnel, pit and cover). Hidden excavated tunnel becomes the only choice in complex conditions because it is suitable. It is inevitable that hidden excavation leads to settlement and influence use of adjacent structure. That is even so when the big span tunnel excavates. This paper analyzes the action mechanism of construction scheme with central boring in controlling settlement according to a case in Beijing. At the same time, it analyzes the value and percent of settlement in each step of center drift method according to monitoring data in site. Finally, center drift method is effective measure to control settlement in big span tunnel and reduces the settlement in 5mm. As a successful case, it may be useful to future similar engineering.