Abstract: The differential equations of variablesection framed-tube structures are derived based on a mathematical model ofan equivalent continuum and the energy variational principle. Every storey with a same section is taken as acalculation element. The element matrix, section matrix and transfermatrix of every element are derived by the differential equations.Then the variable section framed-tube structure is anlyzed by thetransfer matrix method. Finally, a mumerical example is given.