The　metro　tunnel　of　a　newly　constructed　line　that　crosses　underneath　the　tunnel　of　the　existing　line　in　Beijing　has　significant　effects　on　the　adjacent　tunnels.　Based　on　the　FLAC　numerical　model　and　the　stress　release　method,　concerning　on　the　settlement　slot　of　the　existing　metro　tunnel　and　steel　tube　pre-reinforced　construction　of　the　newly　constructed　line,　the　process　of　tunneling　is　simulated　and　the　settlement　of　the　influenced　part　of　the　existing　line　is　obtained.　The　result　is　analyzed　subsequently.　The　conclusions　of　this　paper　may　help　evaluate　the　security　of　the　existing　metro　tunnel,　control　the　construction　process,　and　actualize　the　monitoring　during　tunneling.