Following from the results of sensitivity analysis of standard eigenvalue problems,the differentiability of semisimple multiple eigenvalues of nonsymmetric generalized eigenvalue problems is proved,and the derivatives of semisimple multiple eigenvalues and the series expansions of the corresponding eigenvectors are obtained.On these grounds,the sensitivity of semisimple multiple eigenvalues of generalized eigenvalue problems is defined,and the sensitive elements of matrix pairs can be determined.