AbstractA fitting method is proposed to estimate the anisotropic loss factors of the T700 carbon fibers. In this fitting method, the loss factors of fibers are taken as unknown variables, storage modulus of fibers is assumed to be invariant. The generalized method of cells (GMC) is combined with the correspondence principle to calculate the loss factors of unidirectional carbon fiber reinforced plastics, and the loss factors of fibers are obtained by fitting the loss factors of composite material with the least square method. The loss factors of the T700 carbon fibers obtained by the fitting method are compared with the experiment and verified by the finite element method based on the direct‐solution steady‐state dynamic analysis and the representative volume element. Results show that the fitting method based on the GMC can accurately calculate the anisotropic loss factors of the T700 carbon fibers.