Abstract: A 2-D equivalent circuit of column horn with large aspect ratio is obtained from an approximated solution of vibration equations.It is used in axisymmetric vibration analysis with or without external load,and also used in frequency variation evaluation due to various aspect ratios.Comparison is made with other models such as the finite element and the traditional 1-D models.It has been shown that this model gives a more accurate frequency calculation than the 1-D models,and agrees with the finite element mode analysis.In turn,the frequency associated vibr-ation mode is determined.When water-loaded,axially or circumferentially,vibration frequencies in these two cases are rather close.This model is expected to have a further use in optimizing ultrasound horn.