The invention discloses a low pressure cylinder structure for a steam turbine. The low pressure cylinder structure comprises an upper-half cylinder body, the upper-half cylinder body is sequentially divided into a left steam exhaust zone, a middle steam inlet zone and a right steam exhaust zone in the axial direction according to working characteristics of a low pressure cylinder, a steam inlet is formed in the portion, at the middle steam inlet zone, of the upper-half cylinder body, the steam inlet at the middle steam inlet zone is formed in the upper-half cylinder body in the radial direction in an inwards concaved mode, and the steam inlet at the middle steam inlet zone is lower than the top surface of the portion, at the left steam exhaust zone, of the upper-half cylinder body and the top surface of the portion, at the right steam exhaust zone, of the upper-half cylinder body separately. According to the low pressure cylinder structure for the steam turbine, the working characteristics and working effect of the lower pressure cylinder are not affected, the height of the steam inlet in the upper-half cylinder body of the lower pressure cylinder can be effectively and reliably decreased, and therefore the slinging height of a communicating pipe of the lower pressure cylinder can be directly and effectively decreased; and the capital construction cost of workshops in a power plant can be greatly reduced, and the low pressure cylinder structure is reliable and practical.