Disclosed is a large-span subway station underground excavation construction method for a hard rock stratum. The large-span subway station underground excavation construction method for the hard rock stratum is used for effectively reducing the excavation construction risk and improving the excavation construction efficiency. The large-span subway station underground excavation construction method for the hard rock stratum comprises the following steps that the arch portion middle of a station is divided into two steps to be excavated, a tunnel arch portion middle upper step is excavated, and an initial support arch cover of the tunnel arch portion middle is constructed; a tunnel arch portion middle lower step is excavated; a tunnel arch portion left side portion and a tunnel arch portion right side portion are excavated, feet-lock bolts are constructed at the arch foot positions, the initial support arch cover on the arch top is lengthened through connection, and construction of the initial support arch cover is accomplished; a rock mass arranged below the station is excavated in a slot broaching mode under the protection action of the initial support arch cover, nine portions including upper steps on the left portion, the middle portion and the right portion, middle steps on the left portion, the middle portion and the right portion and lower steps on the left portion, the middle portion and the right portion are excavated, and side wall initial supports of corresponding sections are constructed until the rock mass is excavated to the bottom; and a station body structure is sequentially constructed from bottom to top, and station construction is accomplished.