Abstract: A novel algorithm to calculate the middle curves of tubes is presented,which creates rounded tubes,finds intersection of the tubes and calculates the projection of the intersection.Furthermore,an algorithm to design the turbo-jet blades with unequal thickness based on the middle curve is proposed.By taking the thickness at the featured points on the sectional line as the thickness parameters,the number of the design variables of the blades is decreased to six.It facilitates parametric optimization.With the thickness calculation,four kinds of the turbo-jet blades can be generated.Finally,a parametric CAD system for the turbo-jet blades with unequal thickness is implemented,and some detailed examples are given.