Abstract: An annular transition element is proposed, in which circumferential displacements are represented by Fourier, series. Therefore, it reduces three-dimensional problems into two-dimensional ones and saves computer storage, and time considerably.In dynamic analysis of a thick disc, its inner bub is represented by annular isoparametric elements and its web by annular thick plate elements, the annular transition elements are provided to connect the above two kinds of elements. The combined finite element model is applied to calculating the dynamic characteristics of an actual turbine disc. The results obtained are compared favourably with the experimental data and the analytical results by other finite element models （i. e, annular thick plate elements and sector thick plate elements）.