Abstract: A calculation method is presented to determine the integral strength of a complexrotor with both radial interference and axial pretension. The method is characterized by followings.calculating the flexibilities and free deformations at the connection nodal points of rotor substructures with finite element method at first; determining the inner forces at these points then; obtaining the deformations and stresses of the individual rotor substructures at last. The method is verified by using a conventional finite element method for a modal stage in good agreement. The present method has been applied to the final design of a disk-drum detachablerotor with bidirectional interferences, which consists of profile wheels, annulus spacers and conical shafts. The rotor is designed for a six-stage compressorand is divided into 2504 annular elements of triangular type by 2020 nodal points. The rotor integral strength calculation is performed on a small computer of only 16K memories. The rotor deformation and iso-stress line diagramsare drawn by computer. The mechanical relationship of the rotor with its individual parts is quite clear.