The material modulus is corrected based on the Halpin-Tsai formula according to the structure and deformation characteristics of composite flexbeam. The stiffness of flexbeam is calculated by the blade computer aided desigh (BCAD) special software except for the torsional stiffness which is calculated by the empirical formula. It is proved that the method can im prove the calculation accuracy of the flexbeam section stiffness, and also can guarantee the accuracy of the dynamics and the lord calculation of bearingless rotor/tail rotor.