Abstract: This paper is based on the solution of the target function ηt an optimum parameter selection method of geometrics with some constraints of engineering construction conditions has been offered. These constraint conditions are the maximum allowable centrifugal stress, the form of the meridian passage(may be lqual top diameter equal middle diameter equal root diameter or fixed concrete value of any diameter) the limitation of the passage expansion angle γ,the limitation of the minimumα2, the limitation of the Dm/ L and chord span ratio L/b.In this method a relative new loss model-AMDC-KA has been useb, only one minute　on computer TQ16, we can get a satisfactory result.