Abstract: Based on Beijing Metro Pingguoyuan Station, a construction method for adding overlaying level on the station existing structure is proposed. Results show that the stability of open excavation foundation pit is greatly affected by the station existing structure. Through connecting pile bottom and primary support structure, connecting pile back deep-hole grouting reinforcement and reserved anti-pressure soil, the enclosure structure deformation can be effectively suppressed. To sustain the station structure integrity, the bottom underground-excavated structure should reserve joint heads and conduct super-thick concrete backfilling at the joint. The joints of metro station that adopt SBS (modified asphalt waterproofing roll) lapping connection method will ensure the waterproof performance of the structure.