It often happens that a running tunnel has to cross closely underneath existing Metro structures, which have strict settlement limit. Therefore focus has always been placed on how to effectively control the settlement of the existing Metro structures. The running tunnel from Dongsi station to Chaoyangmen station on Line 6 of Beijing Metro crosses closely underneath Dongsi station of Line 5 of Beijing Metro. Key technologies adopted in the construction of the mentioned running tunnel, including reinforcement and waterstopping by advance grouting, CRD+jack support method, grouting through assistant deep holes, and backfill and compensation grouting, are presented in the paper. The monitoring of existing Dongsi station of Line 5 of Beijing Metro shows that, due to the aforementioned technologies, the deformation of the existing structure has been brought under effective control, which guarantees the tunneling safety and the normal operation of the existing Metro line. 