Abstract: Leading into the four-dimensional wave vector, the transfer matrix and the transmission coefficients of the solid and solid constitute phononic crystal were inferred. Using these formula the transmission coefficient of the longitudinal wave and transversal wave in the solid and solid constitute phononic crystal were calculated. When longitudinal wave oblique incidence, there is the forbidden band of longitudinal wave in the transmission wave, and there is reforming that longitudinal wave to transversal wave, the greater the incident angle is more obvious of the reforming. When transversal wave oblique incidence there is similar result also. Used these formula the transmission and reforming of the elastic wave in the solid and solid constitute phononic crystal are solved.

Key words: Leading into the four-dimensional wave vector, the transfer matrix and the transmission coefficients of the solid and solid constitute phononic crystal were inferred. Using these formula the transmission coefficient of the longitudinal wave and transversal wave in the solid and solid constitute phononic crystal were calculated. When longitudinal wave oblique incidence, there is the forbidden band of longitudinal wave in the transmission wave, and there is reforming that longitudinal wave to transversal wave, the greater the incident angle is more obvious of the reforming. When transversal wave oblique incidence there is similar result also. Used these formula the transmission and reforming of the elastic wave in the solid and solid constitute phononic crystal are solved.