The invention relates to a full arc admission steam turbine, which includes a plurality of nozzle boxes for inducing steam, and a plurality of nozzle plates for bearing nozzles, one nozzle plate corresponding to each nozzle box. The steam turbine 100 further includes a plurality of spacer plates corresponding to the plurality of nozzle boxes, wherein the spacer plate is disposed between the nozzle plate and the nozzle box, by which a flow path is formed between the plurality of nozzle boxes and the plurality of the nozzle plates through the plurality of spacer plates to achieve a full arc admission. With the solution according to embodiments of the present invention, existing partial arc steam turbine may be easily converted to be a full arc admission steam turbine. This will reduce cost of equipment upgrading. Outage due to onsite conversion may be significantly reduced.