To study the mechanical effects of the arch cover method in the construction of large-span underground subway station with upper soft and lower hard excavation, taking the construction of Southeast Mountain Station on Dalian Metro Line 4 as the research background, a research method adjoining numerical simulation and on-site monitoring was adopted. MIDAS-GTS/NX finite element software was used to study deformation and stability of surrounding rock and contrastive analysis with on-site measured data. The research results indicate that surface subsidence shows a decreasing trend from the centerline of the station to both sides, and the affected region is about twice the excavation skip distance of the station. The variant and stress of country rock have apparent symmetrical characteristics, the surrounding rock of the arch is mainly caused by settlement, while the high side wall is mainly uplift, the arch spans invades towards the tunnel clearance, the large arch foot invades towards the surrounding rock; the von mises stress of the country rock is under compression, and there is a phenomenon of concentration of stresses at the closed angle of the arch foot; the location of the plastic region of the country rock change continuously with the build of the depot, and ultimately funnel into the high side walls. The verification of surface settlement is predicted using the Peck formula, and the feasibility of using the arch cover method for construction in upper soft and lower hard strata is verified, which provides a reference for similar practical projects.