Abstract: In accordance with the flow characteristics and possible projects of the transonic turbine, the one dimensional fundamental relations are derived and parametric analysis has been made in detailo The concepts of "trannsonic velocity ratio"Ω is introdced by considering the choking characteristics and is used fo correlate the calculated results and to obtain the optimal values.The relation between the turbine regime and its geometric and aerodynamic parameters is also analized, and so some recommendations are finally given for the proper selection of the design parameters of the transonic turbine.