北京地铁四号线宣武门站是国内首例下穿既有车站施工的暗挖地铁站，由于新站近距离下穿，为保证既有站的正常运营，给施工带来巨大挑战。从数值模拟和施工经验2个方面阐述了该项目施工方案的比选，经随后的施工实践证明，确定的施工方案是合理有效的，此施工方案对今后的下穿既有线施工有一定的参考价值。

Xuanwumen station on No.4 line of Beijing Metro is the first mined tunnel that undercrossing existing station in China. Due to the space between the two stations is too narrow and the existing station must be normal operating, the construction is a huge challenge. The construction schemes selection of this project are analyzed from numerical simulation and construction experience. The successful completion of this project shows that the selected construction scheme is reasonable. This construction scheme can provide reference for the similar projects construction in the future.