The invention comprises a turbine low pressure cylinder structure which comprises an outer cylinder and an inner cylinder. An upper steam exhaust diffusion part and a lower steam exhaust diffusion part are arranged between the outer cylinder and the inner cylinder; the lower half of the outer cylinder and the lower half of a steam exhaust cone are of split structures in the axial direction, the lower half of the outer cylinder and the lower half of the steam exhaust cone are connected and combined through a corresponding flange and locking bolt pair, and the outer end of the lower half of the steam exhaust cone and the outmost end of the lower half of a steam exhaust flow guide ring in a staggered manner; the upper half of the outer cylinder and the upper half of the steam exhaust cone are of split structures in the axial direction, the upper half of the steam exhaust cone and the lower half of the steam exhaust cone are connected and combined through a corresponding flange and locking bolt pair, a matched gap is reserved between the upper half of the steam exhaust cone and the upper half of the outer cylinder, and the outer end of the upper half of the steam exhaust cone and the outmost end of the upper half of a steam exhaust flow guide ring in a staggered manner; and the upper half of the outer cylinder and the lower half of the outer cylinder are installed on a rotor through an expansion joint and an end steam seal in sequence, and the expansion joint extends into the upper half of the steam exhaust cone and the lower half of the steam exhaust cone in the axial direction.