Abstract: Undercutting interval of Jishuitan station-North Taipingzhuang station in the line of the Beijing subway closely crosses underneath the existing tunnel of the Line 2,Due to restrictions on construction conditions,use the method of straight wall.Through the introduction of straight wall structure design,the reason,design method,calculation process,construction process,numerical simulation and key technologies in the design and construction of straight wall are described in detail.Crack width is 0.19 mm,reinforcement rate is 0.6%which shows that the calculation parameters in the design are more reasonable.Numerical simulation analysis shows that cumulative maximum settlement of existing structures is 2.45 mm,the maximum lateral displacement is 0.15 mm which indicate the rationality of the design and construction process.