The paper aimed at a detailed case study of cross-passage, which is forced to design and construct by connecting the station box and main tube tunnel of Marol Naka station in Mumbai Metro Line 3, since the marol Naka is densely populated area and elevated metro line is passing over an underground station, therefore further excavation of tunnel is done through the cross-passage. In these station, the cross- passage is constructed for public utilities for connecting the station box to the platform and also for the emergency exit. During tunnel construction, the cross passage is excavated after the main tunnel has been constructed. At the same time, the safety of the cross passage and the stability of the tunnel must be ensured by instrumentation and monitoring. Design of the cross- passage is achieved according to the principles of “New Austrian Tunnelling Method’ (NATM) and the composite lining structure is adopted. NATM is used to widen the station platform which is initially tunnelled by the TBM. The dimension of 230m long and 15m wide Marol Naka station has 16 cross-passages which are constructed connecting the station box to the platform; the observations and the designing part- Finite Element method is used in order to evaluate stress deformations induced on the cross-passage. Keywords: Cross passage, NATM, TBM, Finite element method, Marol Naka station, Emergency exit.