Abstract: The two-dimensional aerodynamic design and the three-dimensional flowfield analysis,which are two of the three main parts of supersonic/transonic fan aerodynamic design system,do not match in flow model.Therefore,a triangular model of aerodynamic design system is put forward to improve the design system.As a part of its implementation a quantitative indicator is provided which uses the inner flow deviation angle and its deviation to evaluate quantitatively the designed flowfield and to guide the next design iteration.The possibility of developing the indicator into a criteria is also discussed.