Many references are written on the designs of a gas turbine. But there are none which explain the entire design process from stage to stage. Taking type 7000 of Hitachi G.E. gas turbine as a model, its whole design method is shown in this paper. The 7000 type is the most improved and most powerful gas turbine in the G.E. family. The solidity of compressor varies considerably according to the amount of work allotted to each stage. How to distribute most efficiently the work to each stage is described. In turbine design, the most difficult problem is to determine the Mach number of exit velocity c2. How to determine the Mc2 to each stage is explained. Another important value of u/c1 is chosen in this paper, so that the blade root reaction degree is.10. Four gas turbines of this type combined with one steam turbine, so called STAG plant is obtained, which recently attracts wide attention as middle load power plant of a low public nuisance. It gives total 400 Mw, and over 40% net plant efficiency can be expected.
