The inherent frequencies in the first two steps of the model of cantilever plate with an attached lumped mass are calculated by the theoretical equation based on existing theory, then compared the relative results analyzed by finite element software and tested by experiment. The data of these three were found to have good consistency which verified reliability of finite element software in auxiliary calculation. Engineering problems like natural frequencies, inherent vibration modes and amplitudes vibrated by external excitation are analyzed by modal and response spectrum in mature finite element software, in order to avoid complexity of theoretical calculation and difficulty in achieving analytical solution.