Abstract: The line intersection will change the mechanical behavior of existing tunnel during the construction of an expressway crossing over an operating high-speed railway tunnel and endanger the operation safety of the railway tunnel. Based on a practical engineering case, a numerical simulation analysis on the overcrossing intersected section is conducted by MIDAS GTS/NX finite element software, and the changes of mechanical behavior and safety factors of high-speed railway tunnel are studied before and after the load applying of expressway. The results show that the amplitude of stress increase and safety factor decrease of existing tunnel are small after load applying of expressway, and it has a little effect on safety of tunnel structure.