Band gaps of elastic waves in 1-D phononic crystals with imperfect interfaces were studied.By using the transfer matrix method(TMM) and the Bloch wave theory in the periodic structure,the dispersion equation was derived for the periodically laminated binary system with imperfect interfaces(the traction vector jumps or the displacement vector jumps).The dispersion equation was solved numerically and wave band gaps were obtained in the Brillouin zone.Band gaps in the case of imperfect interfaces were compared with that in the case of perfect interfaces.The influence of imperfect interfaces on wave band gaps and some interesting phenomena were discussed. Band gaps of elastic waves in 1-D phononic crystals with imperfect interfaces were studied. By using the transfer matrix method (TMM) and the Bloch wave theory in the periodic structure, the dispersion equation was derived for the periodically laminated binary system with imperfect interfaces the traction vector jumps or the displacement vector jumps. The dispersion equation was solved numerically and wave band gaps were obtained in the Brillouin zone. And gaps in the case of imperfect interfaces were compared with that in the case of perfect interfaces. The influence of imperfect interfaces on wave band gaps and some interesting phenomena were discussed.