Abstract: The settlement of the ground surface is one of the most concerned engineering problems in subway shield tunneling, because the settlement is in relation to the usual operation of adjacent structures and the normal proceeding of shield construction. Therefore, this paper takes the ground surface settlement as the key objective to decide the shield parameters. The parameters affecting the surface settlement are simplified into two indices, namely support pressure ratio on the tunnel face to the earth pressure and the elastic modulus of generation layer. Taking the section from Nanmenkou to Houjiatang along Line 1 of Changsha Metro as an example, this paper carries out FLAC^3D numerical simulation to analyze the effects of the two indices on surface subsidence. The suggestion of the shield parameter values for the selected section of Changsha subway is then put forward. Besides, the subsiding area and the maximum of the subsidence are also proposed. This research brings out a reference for the subsequent construction of Changsha metro and provides a method for parameter deciding of shield tunneling in other cities.