A　simplified　mechanical　model　of　vertical　vibration　of　the　pipe　pile　embedded　in　radially　inhomogeneous　and　longitudinally　layered　viscoelastic　soil　considering　both　the　variations　of　cross-section　and　modulus　along　the　pile　shaft　is　proposed,　by　employing　the　viscous　damping　model　and　the　plane　stain　model　of　annular　complex　stiffness　transfer.　Firstly,　the　complex　stiffness　at　the　interface　between　soil　and　pile　is　derived　based　on　Laplace　transform　and　complex　stiffness　transfer　method.　Secondly,　the　analytical　solutions　for　dynamic　impedance,　velocity　admittance　and　reflected　wave　signal　at　the　pile　head　are　obtained　by　using　the　pile-soil　compatibility　condition　of　pipe　pile　and　radial　inhomogeneous　surrounding　soil.　Furthermore,　the　obtained　analytical　solution　for　dynamic　impedance　at　the　pile　head　is　also　reduced　to　verify　its　validity　with　existing　solution.　Finally,an　extensive　parametric　analysis　is　conducted　to　investigated　the　effects　of　the　defective　pile　segments　with　variable　modulus,　necking　and　expanding,　and　the　corresponding　defect　locations　of　pile　shaft　on　the　dynamic　response　at　the　pile　head　of　the　pipe　pile　embedded　in　radially　inhomogeneous　and　longitudinal　layered　viscoelastic　soil,　which　can　provide　reference　and　guide　for　specific　engineering　practice.　©　2018,　Nanjing　Univ.　of　Aeronautics　an　Astronautics.　All　right　reserved.