The method of nondestructive testing of composite beams is discussed by using the operation mode analysis method of the transmissibility functions, by fitting the least squares of the acceleration transfer function, the frequency and damping are obtained,the mode shape is obtained by decomposing the singular value. Curvature mode shape (CMS) and curvature mode shape change rate (CMSI) are presented as damage indexes, modal analysis of composite beam structures with single, multiple and different damage degrees.The results show: the location and size and multiple damage of the damage can be identified. The transverse coordinates can reflect the location of the damage, and the spacing of the mutated units can reflect the size of the damage; the mutation extreme difference of the CMS and CMSI were found to increase with increasing damage degree, demonstrating that the CMS and CMSI has the ability to quantitatively identify damage degree; Compared with the CMS, the CMSI is more sensitive to the composite beams damage.